Sand Filter

Sand filters remove suspended particles and contaminants from pool water, delivering clear and transparent water. In the following, we’ll review the types, capacity estimation methods, technical specifications, and pricing. (Since 2004)

Expert Guide to Selecting and Pricing Pool Sand Filters

A sand filter is a key component in pool water treatment systems, responsible for removing impurities and improving water quality. Sand filters are typically made from galvanized steel or fiberglass and are available in two designs: vertical cylindrical and horizontal.

The operation of a sand filter is based on physical filtration. As water passes through the filter, impurities are trapped by graded silica sand, and the filtered water returns to the pool. The silica media is graded to effectively remove fine particles and contaminants.

Overall, sand filters have a wide range of applications and are used in both residential and industrial pools. Their presence is essential as they ensure swimmer safety and water cleanliness.

Ultimately, with its engineered structure and high efficiency, a pool sand filter is considered one of the most important components of a pool water treatment system.

What Is a Sand Filter?

A sand filter is a system used for water treatment and the removal of suspended particles, contaminants, and impurities from water. These filters are made up of multiple layers of sand and gravel with different grain sizes. As water passes through these layers, solid particles and pollutants are trapped. Purchasing a sand filter is an ideal option for improving water quality due to its high efficiency, low maintenance cost, and wide application in swimming pool water treatment, agricultural systems, and industrial processes. Using a pool sand filter not only helps maintain water hygiene but is also compatible with environmental standards.

When purchasing a sand filter, factors such as tank material, tank capacity, operating pressure, silica quality, and the manufacturer’s brand should be carefully considered, as each of these directly affects the unit’s performance and price. Well-known brands such as Araz Sanat, Emaux, Hiwater, Damatajhiz, and Megapool offer models with a wide range of capacities and prices.

How a Pool Sand Filter Works

The operating principle of a pool sand filter is as follows: pool water is first pumped into the filter tank and then passes through the sand layers inside the filter. The sand media traps suspended particles and dirt, and the clean water is returned to the pool through the outlet. For proper operation, the sand surface must be level, and at specific intervals, the filter requires monthly backwashing to remove the accumulated debris from the sand bed.

When the pressure on the filter gauge increases or the water flow rate decreases, this indicates that the sand media is saturated and monthly backwashing is required. This process maintains filter performance and prevents damage to the pump and filtration system. Understanding how a pool sand filter works helps users correctly inspect and maintain critical components such as multiport valves, inlet and outlet valves, and sand layers.

A pool sand filter usually consists of several sand layers with different particle sizes; the top layer captures larger particles, while the lower layers filter finer impurities. Maintaining this structure and performing regular maintenance ensures optimal filter efficiency and clear pool water.

Applications of Sand Filters

One of the most widely used pieces of pool water treatment equipment is the pool sand filter, which improves water quality for various applications by removing suspended particles, contaminants, and impurities. Due to their high efficiency, low maintenance cost, and long service life, these filters are considered an ideal choice for residential, industrial, and agricultural uses. Below, we review the main applications of pool water filters:

1. Swimming pool water filtration
2. Removal of dissolved colors in water
3. Treatment of return water from cooling towers
4. Filtration of water in fish farming pools
5. Treatment of industrial and domestic wastewater
6. Filtration of surface water (river or well water)
7. Pre-treatment in reverse osmosis (RO) systems
8. Filtration for potable and industrial applications (urban and industrial water treatment)

Sand Filter Components

In general, a sand filter consists of a set of specialized components, each of which plays an important role in the water treatment process. These components operate in coordination to ensure effective and stable filtration performance:

Filter Tank

The main tank of a sand filter is made of galvanized steel, stainless steel, or fiberglass (FRP) and houses the sand bed. This tank must have sufficient resistance to operating pressure and temperature to ensure long-term durability of the filter.

Sand Bed (Silica)

The most critical part of the filter is the sand and silica layers. This bed typically consists of several layers with different grain sizes that physically trap suspended particles and contaminants. The quality and grain size of the silica have a direct impact on filter efficiency.

Nozzles and Distributors

Nozzles or water distributors are installed at the bottom of the tank and ensure uniform water flow. Some filters use a Double Dish system to improve flow distribution, allowing the entire sand bed to be evenly engaged.

Inlet and Outlet Pipes

Water enters the filter through the inlet pipe and exits through the outlet pipe after passing through the sand bed. The size and material of these connections must be selected according to the operating pressure and filter capacity.

Backwash System

To clean the sand bed of trapped particles, filters are equipped with a backwash system. This system extends the lifespan of the sand media and maintains filtration quality.

Control Valves and Auxiliary Fittings

Multiport valves and fittings related to pressure gauges and flow meters make it easy to control water flow and perform backwashing operations. These components enable safe and stable filter operation.

Supports and Mounting Structure

Sturdy bases and crane lifting lugs facilitate installation and relocation of the filter and prevent damage to the tank during installation.

Pool Sand Filter Price List

If you are looking to purchase a pool sand filter with the best price and quality, Damatajhiz is one of the most reputable specialized suppliers in the Iranian market. At this company, you can compare and select various pool sand filters from well-known domestic and international brands such as Hiwater, Emaux, Megapool, Araz Sanat, and other leading manufacturers.

The price of pool sand filters in Bahman 1404 varies depending on the brand, capacity, tank material (fiberglass, metal, or stainless steel), and the required pool size. To help you make a more accurate choice, the table below presents the approximate price ranges of different sand filters, allowing you to find the most suitable option based on your budget and application.

Sand Filter Brand	Description	Approximate Price (USD)
Hiwater Sand Filter	Good build quality, durable fiberglass body, wide model variety	132 - 420
Damatajhiz Sand Filter	Extensive after-sales service, wide brand selection, high availability	276 - 5082
Araz Sanat Sand Filter	High durability, suitable for industrial projects and large pools, cost-effective compared to foreign alternatives	660 - 1089
Emaux Sand Filter	Elegant and durable design, easy installation, spare parts availability	155 - 439
Megapool Sand Filter	High resistance to UV and chlorine, local after-sales service, multiple models	252 - 530
Ariona Sand Filter	Excellent quality, durable body, wide model variety	Upon Inquiry

Please note that the pool sand filter prices provided by Damatajhiz are up to date, and applicable customer discounts have already been applied to these prices.

Factors Affecting the Price of Sand Filters

The price of a pool sand filter depends on various factors, each of which plays an important role in determining the final cost of this water treatment equipment. When purchasing a pool sand filter, reviewing these factors helps you make an accurate and cost-effective choice.

The most important factors affecting the price of a sand filter include:

Sand Filter Body Material

The filter body may be made of fiberglass, metal (stainless steel or galvanized steel), or polyethylene. Metal sand filters generally have higher durability, but their price is usually higher than fiberglass models.

Filter Capacity and Dimensions

The greater the capacity and size of the sand filter, the higher the amount of silica required, the filtration volume, and consequently, the price of the sand filter.

Operating Pressure and Filtration Type

High-rate pressurized sand filters are more expensive than gravity or slow-rate filters due to their stronger design and higher filtration capacity.

Brand and Country of Manufacture

Well-known international brands such as Emaux and Hiwater are generally more expensive than domestic brands like Araz Sanat or Megapool; however, they offer higher durability and efficiency.

Accessories and Multiport Valve

The presence of auxiliary equipment such as a multiport valve, pressure gauge, nozzles, and base directly affects the increase or decrease in the sand filter price.

Warranty and After-Sales Service

Brands that provide reliable warranties and after-sales services usually have higher prices, but they are more economical in the long term.

Ultimately, the price of a pool sand filter is not limited solely to its dimensions; build quality, manufacturer brand, operating pressure, and application type also affect the final cost. To check the latest sand filter prices and choose the best model based on your needs, you can refer to the specialized Damatajhiz collection.

Problems Caused by Not Using Pool Sand Filters

Failure to regularly filter pool water can cause serious health and hygiene problems, including:

• Stagnation and contamination of water due to the open pool surface
• Entry of foreign materials such as leaves, soil, and dust into the water
• Growth and proliferation of germs and various microbial fungi
• Presence of parasite eggs in pool water
• Occurrence of diseases such as typhoid fever, jaundice, and digestive disorders

These issues clearly show how harmful the absence of a pool sand filter can be.

Types of Sand Filters

Pool sand filters are manufactured in various models based on body material, operating method, capacity, dimensions, number of silica layers, and installation method. Each type of sand filter has its own specific application and features, and selection should be based on pool water volume and intended use.

In general, the main types of pool sand filters include:

• Metal sand filter: Made of steel with an anti-corrosion coating, suitable for large and industrial pools.
• Fiberglass (FRP) sand filter: Lightweight body, resistant to corrosion and UV radiation, suitable for residential and semi-industrial pools.
• Galvanized sand filter: Made of hot-dip galvanized steel sheets and highly resistant to moisture.
• High-rate (pressurized) sand filter: Capable of rapid water filtration in a shorter time, used in high-flow filtration systems.

Damatajhiz; Thousands of Products for Thousands of Projects Across the Middle East (Since 2004)

Types of Industrial Sand Filters Based on Body Material

One of the key criteria for classifying sand filters is their body material. This material must be capable of withstanding pressure, temperature, corrosion, and other environmental factors. Below are the types of sand filters categorized by body material.

Metal Sand Filter

Sand filters with metal bodies are among the most durable and stable types of filters when exposed to high pressure and temperature. Their exceptional ability to withstand pressure and heat, along with wide industrial applications, are considered key features of these filters.

However, pool sand filters with metal bodies perform poorly when exposed to moisture and corrosive substances and have lower durability under such conditions. Additionally, due to their heavy weight, transportation, installation, and maintenance can be more challenging.

An important point is that metal sand filters offer higher filtration power compared to fiberglass filters. In contrast, fiberglass filter bodies have lower resistance; therefore, metal filters are more commonly used in high-temperature environments.

Fiberglass (FRP) Sand Filter

Another type of this equipment is the fiberglass sand filter, also known as the FRP sand filter. These filters are often used instead of galvanized and metal models because they do not suffer from disadvantages such as heavy weight and low resistance to moisture.

Fiberglass materials have higher resistance to corrosive substances, and their lighter weight makes transportation and installation much easier.

However, these filters have lower resistance to impact, pressure, and heat compared to metal types. In addition, if the body is damaged, repair is usually not possible and replacement is required.

Horizontal Galvanized Sand Filter

The horizontal galvanized sand filter features a cylindrical tank mounted horizontally on multiple supports. Naturally, due to its horizontal installation, this type of sand filter occupies a relatively large floor area. Horizontal galvanized sand filters are suitable for environments with limited ceiling height but sufficient floor space in the mechanical room for filter installation.

Comparison of Metal and Fiberglass Pool Sand Filters

Metal and fiberglass (FRP) sand filters are among the most commonly used water filtration equipment, each with its own features and applications. Metal filters are suitable for high-pressure industrial applications, while fiberglass filters are ideal for general uses such as swimming pools due to their lightweight structure and corrosion resistance. In the table below, these two types of filters are compared in terms of material, cost, weight, maintenance, and application.

Feature	Fiberglass (FRP) Sand Filter (m²)	Metal Sand Filter (m²)
Material	Steel or stainless steel	Resin-reinforced fiberglass
Corrosion Resistance	Moderate (requires anti-corrosion coating)	High (resistant to rust and chemicals)
Initial Cost	Medium to high	Usually lower
Weight	Heavy	Lightweight
Installation & Transportation	More difficult due to heavy weight	Easier due to low weight
Service Life	15–20 years with proper maintenance	20–30 years
Application	Heavy industries, high-pressure operation	Pool water filtration, general applications

Advantages and Disadvantages of Galvanized Sand Filters

Galvanized-body sand filters, due to their metal structure, usually have a higher sand bed capacity compared to polymer models. These filters are resistant to operating pressure and can be easily operated with almost any type of pool pump.

The biggest drawback of metal and galvanized sand filters is body corrosion. In pool water, due to the presence of disinfectants such as chlorine and salt, most metal equipment—if not made of stainless steel (such as 304 or 316)—gradually corrodes over time. This issue was common in older galvanized models, sometimes causing iron rust to enter the pool water. In addition, their heavy weight compared to polymer filters makes transportation and installation more difficult. For these reasons, the use of galvanized sand filters in swimming pools has become less common today.

Advantages and Disadvantages of Fiberglass or Polymer Sand Filters

Polymer and fiberglass sand filters are available on the market in a wide range of sizes and are equipped with modern multiport (six-way) valves. These filters are lightweight, making installation and relocation easier. Most importantly, fiberglass and plastic bodies are highly resistant to continuous contact with chlorinated water and other chemicals, and they do not corrode or rust.

Failures in polymer sand filters are usually related to the valve or the body. To prevent damage, valve position changes should only be performed when the pump is turned off. Additionally, using high-power pumps with filters that have low operating pressure may cause body cracking. Ultimately, timely and regular backwashing ensures proper performance and extends the service life of internal components.

Types of Sand Filters Based on Operation

Sand filters are among the most widely used water filtration systems and are classified into different categories based on their operating method and the speed at which water passes through the sand bed. The force required to push water through the nozzles and sand bed is the main factor determining the filter’s operating type. Below, in addition to the previously explained rapid sand pressure filter, we take a closer look at other types of sand filters, including the slow sand filter, rapid gravity sand filter, and rapid sand pressure filter, along with their features and applications.

Rapid Sand Pressure Filter

The rapid sand pressure filter is one of the most common and effective water treatment devices used to remove suspended particles and impurities from water. These filters utilize sand and gravel beds to remove particles of various sizes, and due to their high operating pressure, they offer very high filtration speed.

Structure and Components of the Rapid Sand Pressure Filter

Pressure sand filters are typically designed in a vertical configuration with dished heads and are manufactured from ST-37 steel sheets or galvanized steel. The upper and lower heads are designed using the DOUBLE-DISH method and, after rust removal, are coated with two layers of internal epoxy and one external stainless-steel layer to enhance durability and resistance. In addition, sandblasting is performed before painting to improve filtration quality and extend service life.

Internal Operation of the Rapid Sand Pressure Filter

At the top of the filter, nozzles are installed to evenly distribute water over the sand bed. At the bottom, brass or plastic strainers collect and direct the filtered water. Inside the filter, three layers of silica sand with specific grain sizes and purity are used, including:

• Grade 1 silica with a diameter of 0.5 to 1.5 mm
• Grade 2 silica with a diameter of 2 to 3.5 mm
• Grade 3 silica with a diameter of 4 to 8 mm

These layers are selected with a uniformity coefficient of 1.35 and a purity of over 95%, filling approximately 60% of the filter tank volume.

Advantages of Purchasing a Rapid Sand Pressure Filter

The rapid sand pressure filter is considered one of the most efficient types of pool water filtration systems. With fast operation and high efficiency, it is designed to treat large volumes of water in a short period. Key advantages include:

High filtration speed: Capable of processing large volumes of water in a short time, ideal for public and industrial pools.

High treatment capacity: Effective removal of suspended particles and impurities on a large scale.

Easy installation, commissioning, and maintenance: Simple design with easy access to internal components for routine servicing.

High resistance to operating pressure: Robust construction ensures stable performance under high pressure.

Slow Sand Filter

Slow sand filters are among the oldest and simplest water filtration methods and operate without high pressure or complex equipment. In this system, water passes through the sand bed at a very low rate (approximately 0.1 to 0.4 meters per hour). This slow flow allows filtration to occur naturally, mainly through biological processes.

• Biological layer (Schmutzdecke): A layer of microorganisms forms on the surface of the sand bed, helping remove organic and microbial contaminants.
• No need for high-pressure pumps: These filters usually operate without mechanical pressure, relying on gravity to drive water flow.
• Simple maintenance: They do not require complex equipment but need periodic cleaning of the sand bed surface.

Advantages of Purchasing a Slow Sand Filter

The slow sand filter is one of the oldest and most effective methods of natural water purification. Due to its biological operating mechanism, this type of filter not only removes suspended particles but also has a high capability to eliminate pathogenic microorganisms. The main advantages of the slow sand filter include the following:

High filtration quality: Thanks to the biological processes occurring within the sand layers, these filters are highly effective in removing bacteria, viruses, and organic compounds.

Low operating cost: They do not require high-pressure pumps; therefore, their energy consumption is very low.

Suitable for rural and low-infrastructure areas: Simple design and operation without the need for complex equipment make this filter an ideal option for areas lacking industrial infrastructure.

Applications of Slow Sand Filters

Slow sand filters are mainly used in municipal and rural water treatment systems and drinking water purification systems with low to medium capacity. These filters are highly effective in removing biological contaminants and suspended solids and are popular in many developing countries due to their low cost and high efficiency.

Rapid Gravity Sand Filter

Rapid gravity sand filters are another type of sand filter that operate at a higher rate compared to slow sand filters (filtration rates between 5 and 15 meters per hour). These filters use gravity to pass water through the sand bed and do not require high-pressure pumps, while still providing a high filtration rate.

• Sand bed structure: The sand bed in these filters is usually composed of finer-grained sand and is sometimes combined with layers of anthracite coal or garnet.
• Backwashing: These filters require periodic backwashing to release particles trapped within the sand bed.
• Need for pre-treatment: For optimal performance, the incoming water usually requires pre-treatment (such as coagulation or sedimentation).

Advantages of Rapid Gravity Sand Filters

The rapid gravity sand filter is one of the most widely used types of water filtration systems, commonly applied in municipal and industrial water treatment plants to remove suspended particles and reduce water turbidity. These filters operate using gravitational force without the need for high pressure and offer high efficiency.

The main advantages of rapid gravity sand filters include:

High filtration rate: Suitable for treating large volumes of water in a short time and ideal for high-flow systems.

High efficiency in removing suspended solids: Effective capability in reducing turbidity and removing solid particles from raw water.

Simple and cost-effective design: Easier installation and commissioning compared to pressure filters, with lower maintenance costs.

Applications of Rapid Gravity Sand Filters

Rapid gravity sand filters are widely used in municipal water treatment plants, industrial systems, and high-capacity water treatment facilities. These filters are typically used alongside other treatment processes (such as chlorination) to ensure drinking water quality.

DamaTajhiz; Guide to Choosing and Buying HVAC Systems and Building Facilities in the Middle East (Since 2004)

Performance Comparison of Different Types of Sand Filters

To select the best pool filtration system, understanding the differences and performance of various types of sand filters is essential. In this section, different sand filter models are reviewed and compared in terms of efficiency, durability, maintenance cost, and application in residential and public swimming pools to help you make a more accurate and informed decision.

Filter Type	Filtration Rate (m/h)	Main Mechanism	Main Application	Advantages	Disadvantages
Rapid Sand Pressure Filter	10–20	Pump Pressure	Swimming pools, industrial and residential facilities	High speed, suitable for large volumes	High cost, complex maintenance
Slow Sand Filter	0.1–0.4	Gravity, biological process	Drinking water treatment, rural areas	High quality, low operating cost	Low speed, requires large space
Rapid Gravity Sand Filter	5–15	Gravity	Municipal water treatment plants, industries	Reasonable speed, economical installation cost	Requires backwashing and pre-treatment

Key Points in Selecting the Type of Sand Filter

Selecting a suitable sand filter depends on several factors that must be evaluated based on operating conditions and project requirements:

1. Required Water Volume

• For large volumes and high flow rates, the use of rapid pressure sand filters or gravity-type sand filters is recommended.
• For smaller volumes, conventional sand filters can also provide sufficient performance.

2. Quality of Incoming Water

• If the incoming water contains biological contaminants (such as bacteria or algae), a slow sand filter is a more suitable option due to the longer water retention time.
• For removing suspended solids and turbidity from typical water, rapid pressure sand filters are more efficient.

3. Available Space and Costs

• Slow sand filters require larger space and higher initial investment costs.
• Pressure sand filters have a more compact design and are more suitable for limited spaces.

4. Purpose of Filtration

• For drinking water: a slow sand filter or a combination of a rapid sand filter with a disinfection system (such as chlorination or UV) is the best choice.
• For swimming pools and industrial applications: pressure sand filters are recommended due to higher efficiency and easier backwashing.

Overall, selecting the appropriate type of sand filter should be based on water volume, inlet water quality, space limitations, and the filtration objective, ensuring high efficiency while optimizing maintenance and operating costs.

Sand Filter Media Grading Arrangement

To achieve maximum filtration efficiency, the sand filter bed should be arranged in layers using silica media with an appropriate uniformity coefficient (UC) and a purity of over 95%. The standard three-layer configuration is as follows:

Grade 3 Sand (Coarse):

• Installed at the bottom of the filter, accounting for approximately 20% of the total bed volume
• Particle size typically between 4 and 8 mm
• Main function: acting as a support layer for upper layers and preventing large particles from reaching the nozzles

Grade 2 Sand (Medium):

• Located in the middle section of the filter, accounting for about 20% of the total bed volume
• Particle size ranging from 2 to 3.5 mm
• Main role: capturing and separating medium-sized particles and helping to reduce excessive pressure on the top layer

Grade 1 Sand (Fine):

• Placed in the upper section of the filter, forming approximately 60% of the total tank volume
• Particle size between 0.5 and 1.5 mm
• Main function: removing fine and suspended particles from water and ensuring high filtration quality

Proper design of this media grading allows water to flow uniformly through the sand bed, minimizes nozzle clogging, and maintains the hydraulic capacity of the filter within standard limits.

Design and Capacity Calculation of Sand Filters

Designing a sand filter is an engineering process that requires consideration of several key hydraulic and operational parameters. The most important of these parameters is the linear water velocity (Filtration Velocity), which plays a decisive role in determining the filter diameter and cross-sectional area.

Calculation of Pool Water Volume

The first step in selecting a sand filter is calculating the pool water volume. The volume calculation varies depending on the geometric shape of the pool:

• Rectangular or square pools

 Volume = Length * Width * Depth

 

• Circular pools

 

 V = h * r³ * π

Where r is the radius and h is the pool depth.

Example: If we have a rectangular pool with a length of 10 meters, a width of 5 meters, and an average depth of 2 meters, the volume will be:

 V = 10 * 5 * 2 = 100 Cubic meter (m³)

Calculation of Water Turnover Rate

The turnover rate indicates the time required for the entire pool water volume to pass through the filter once. This rate varies depending on the type of pool:

• Residential (private) pools: once every 6 hours
• Private outdoor pools: 3 to 4 times per day
• Public pools: due to higher contamination, usually every 4 to 6 hours or more frequently
• International standards recommend that water in private pools should pass through the filtration system at least 4 times per day.

Calculation of the Required Flow Rate for a Sand Filter

After calculating the pool volume and circulation rate, the sand filter flow rate must be determined. The flow rate indicates how much water should pass through the filter per hour or per minute.

 Q = V/t

• Q = Flow rate (cubic meters per hour)
• V = Pool volume (cubic meters)
• t = Complete water turnover time (hours)

Example: If the pool volume is 100 cubic meters and we want the entire water volume to be filtered once every 5 hours.

 Q = 100/5 = 20 m³/h

Selection of Sand Filter Diameter and Height

After determining the flow rate, a suitable sand filter must be selected. The filter dimensions are calculated based on the following standards:

• Metal Sand Filter
  For every 0.93 square meters of filter surface area, approximately 20 liters per minute of flow rate is considered.
• Fiberglass (FRP) Sand Filter
  For every 0.93 square meters of filter surface area, it provides between 60 to 75 liters per minute of filtration capacity.
• Filter Height
  It is usually considered to be 1.2 times the filter diameter to ensure optimal performance of the silica bed.

Selection of the Appropriate Silica Media

For proper operation, a sand filter requires three layers of silica with different grain sizes:

• Grade 3 Sand (Coarse): 20% of the tank volume, at the bottom of the filter
• Grade 2 Sand (Medium): 20% of the volume, in the middle section
• Grade 1 Sand (Fine): 60% of the volume, at the top of the filter

This combination ensures that coarse, medium, and fine particles are fully captured, resulting in clear and transparent water.

Review of Operating Pressure and Filter Body Material

To select the appropriate capacity, the pump operating pressure and the filter body material must also be considered:

• Metal filters for high-pressure applications and public pools
• FRP filters for residential and semi-public pools
• Galvanized filters for small and cost-effective projects

Schematic Layout of a Pool Sand Filter

This schematic shows how the pool sand filter is positioned within the pool water circulation system. Water is drawn from the pool by the pump, enters the sand filter, suspended particles and impurities are trapped in the sand bed, and the treated water is then returned to the pool.

 

1. Skimmer – Collects surface water and floating debris.
2. Main Drain – Discharges water and settled particles from the pool floor.
3. Overflow Grille – Directs overflow surface water into the filtration system.
4. Pool Pump – Provides pressure and circulates water within the filtration circuit.
5. Sand Filter – Removes suspended particles and clarifies the water.
6. Surface Thermostat – Regulates and controls pool water temperature.
7. Pool Heat Exchanger – Heats pool water using the supplied hot water.
8. Burner – Supplies thermal energy to heat the boiler water.
9. Hot Water Boiler – Produces and stores the hot water required for the heat exchanger.
10. Circulation Pump – Circulates hot water between the boiler and the heat exchanger.
11. Inline Chlorinator – Disinfects and sanitizes pool water.
12. Pool Nozzle – Returns filtered and heated water to the pool.
13. Pool Ladder – Provides easy access and entry into the pool.
14. Pool Light – Provides illumination and enhances pool aesthetics at night.

Factors Affecting Sand Filter Performance

In physical filtration, many factors influence the proper performance of sand filters. The most important factors for achieving maximum filtration efficiency are as follows:

1. Grain size and shape of the particles forming the sand filter media
2. Water flow velocity through the media: The quality of filtered water does not depend solely on flow velocity, but the water flow rate and the number of suspended particles are directly related to operating time between two backwash cycles and pressure drop in the sand filter. Pressure drop indicates that the pores of the filter bed have become clogged with suspended solids and sludge.
3. Filter backwashing method: Depending on the filter type and dimensions, backwashing may be performed using water alone or using both water and air. During water backwashing, the water velocity and pressure must be sufficient to expand the filter bed volume by about 15%, allowing trapped particles to separate and be discharged. In large-size filters, water alone is not enough to agitate the sand bed; therefore, air is used to stir the filter media. For this reason, up to 60% of the total sand filter volume is filled with silica media, and not more.
4. It should also be noted that the power of the pool water filtration pump must be selected so that the water pressure does not excessively disturb the silica bed, preventing sudden discharge of silica or sand from the filter into the pool basin.

What Is Backwash?

The backwash process, also known as reverse washing, is performed regularly—typically on a monthly basis—to clean and remove physical contaminants accumulated between the silica sand layers in a sand filter. This process is controlled and executed by a multiport valve, which is a type of rotary valve.

In sand filters equipped with a pressure gauge, the need for backwashing can be identified by an increase in pressure. For sand filters without a pressure gauge, there is no fixed schedule, and depending on the level of physical contamination such as dust—especially in outdoor pools and during swimmer usage—this process may be performed weekly or monthly.

An important point regarding pool sand filter backwashing is that the operation must continue until the outlet water becomes completely clean and clear.

Pool Sand Filter Backwash Instructions

To perform backwashing, follow these steps:

• Turn off the pool pump.
• First, make sure the pump is switched off.
• Set the filter valve to the Backwash position.
• Place the multiport valve in backwash mode.
• Turn on the pump.
• Water now flows from the bottom to the top of the filter, and the contaminants trapped between the sand grains are flushed toward the drain.

Backwash Duration

This process usually takes 2 to 3 minutes (until the outlet water becomes clear).

Rinse Stage (Rinse)

After completion, turn off the pump, set the valve to the Rinse position, and run the pump for about 30 to 60 seconds to prevent dirty water from returning to the pool.

Return to Filter Mode (Filter)

Finally, turn off the pump and set the valve back to the Filter position. The system is now ready for normal pool water filtration.

When Should Sand Filter Backwashing Be Performed?

When the filter pressure gauge shows a significant difference between inlet and outlet pressure.

Generally, depending on water quality and pool usage, backwashing should be performed every 1 to 2 weeks.

In outdoor pools, due to the entry of leaves, dust, and environmental contaminants, it is recommended to backwash the pool sand filter twice a week.

• Advantages of Regular Backwashing
• Extended service life of the pool sand filter
• Improved water quality and clarity
• Prevention of excessive pressure on the pump and filtration system
• Reduced long-term maintenance and repair costs

Pool sand filter backwashing is one of the most essential pool maintenance operations, as it cleans the silica sand media and increases overall system efficiency.

By following a proper backwashing schedule—especially in outdoor pools—you can always maintain clear, healthy water free of suspended particles.

Multiport Valve for Sand Filters

As mentioned earlier, the various operating modes of a swimming pool sand filtration system can be adjusted using a multiport valve. Please note that when changing the position of the multiport valve or any valves related to the piping circuit, the filtration pump must be turned off. Failure to do so is similar to shifting gears in a car without using the clutch and may cause serious damage to the system.

Depending on their application, sand filters are supplied with two-way, four-way, or six-way valves, and in some cases, these valves must be purchased separately.

Below, the operation of a six-way valve is explained so that all possible modes incorporated into a multiport valve are fully introduced to you.

Filter Mode

The multiport or multi-position valve is set to the Filter mode about ninety percent of the time. In fact, whenever the sand filter is performing its primary function—namely, filtering the swimming pool water—the multiport valve must be set to the Filter position.

In Filter mode, pool water is drawn in by the pump and directed to the valve, then passes through the various layers of silica sand in the filter, where contaminants and suspended particles are removed, and the cleaned water is continuously returned to the pool.

Backwash Mode

To perform reverse washing of the sand filter, the valve is set to the Backwash mode. In this position, pool water is drawn in by the pool filtration pump, passes through the filter in reverse, and is discharged to the drain.

Rinse Mode

For proper cleaning of the sand filter and after completing the backwash process, the multiport valve must be set to the Rinse position.

In Rinse mode, pool water enters the pump and flushes the surface of the filtration bed and the sand filter tank, then is finally directed to the drain. Only after completing the Rinse operation can the cleanliness of the sand filter be ensured.

Waste Mode

Whenever the concentration and accumulation of debris and contaminants in pool water are very high—such as when reopening a pool after a long shutdown period—the multiport valve is set to the Waste mode.

In such conditions, the Filter mode is not capable of handling the large volume of grease and contaminants present in the piping system. By using the Waste mode, dirty pool water is drawn in by the pump and discharged directly to the drain without passing through the filter.

Recirculate Mode

The valve is set to this mode only when disinfecting chemicals have been added directly to the pool water and it is undesirable to reduce the effectiveness of these often expensive chemicals.

In Recirculate mode, pool water containing disinfectants passes through the pump and returns directly to the pool without entering the filter, ensuring that the effectiveness of the chemical treatment is not reduced.

Winter Mode (Winter or Closed)

In Winter mode, all inlets of the multiport valve are closed and the pool is prepared for shutdown. In fact, the Winter position is used to completely prevent water from entering the multiport valve.

One very important point regarding changing the positions of the six-way valve—previously mentioned as well—is that for every mode change, the pool filtration pump must first be turned off. Keeping the pump running during valve adjustment can damage the valve gaskets.

DamaTajhiz; Providing HVAC Systems and Equipment Across the Middle East (Since 2004)

Buying a Swimming Pool Sand Filter

Selecting and purchasing a swimming pool sand filter is one of the most important steps in designing and operating a water filtration system. This choice depends on several factors, including the water flow rate, which must be compatible with the pump capacity. In practice, the selected filter must have a filtration capacity at least equal to the capacity of your pump.

Another important factor is the type and volume of the pool. Small residential pools require more compact filters, whereas public pools or sports complexes with a high number of swimmers require filters with larger capacities to keep the water filtration time within standard limits. In addition, the time required for complete water circulation in the pool is another key parameter that should be considered before purchase.

In summary, accurate calculation of the required capacity and selecting a filter that matches the actual conditions of the pool is a crucial step in maintaining water quality and extending the lifespan of the equipment.

To simplify this process, DamaTajhiz provides the technical specifications and detailed information for dozens of swimming pool sand filter models from reputable domestic and international brands, all offered with original warranties. Users can compare models and receive expert consultation to ensure a reliable and cost-effective purchase.

Most Popular Brands for Buying Swimming Pool Sand Filters

Choosing and purchasing a high-quality sand filter for a swimming pool plays a vital role in water filtration and clarity. Various brands are available on the market, each offering specific features and advantages. The table below presents the most popular swimming pool sand filter brands in Iran along with their key characteristics.

Brand	Key Features	Suitable Application
Hyper Pool	Rust-resistant and moisture-proof, modern design	Residential and public pools
HiWater	High build quality, wide model range, reliable performance	Public and large pools
Emaux	Advanced design, excellent performance, suitable for large pools	Residential and public pools
Araz Sanat	Domestic production, corrosion-resistant, affordable price	Residential and public pools
DamaTajhiz	Domestic production, valid warranty, after-sales service	Residential and public pools
Mega Pool	Domestic production, robust design, suitable for large pools	Public and large pools
Hayward	Durable fiberglass design, easy installation and maintenance, high performance	Residential and public pools

Depending on the type of pool and your available budget, you can choose the most suitable brand. Brands such as Emaux and Mega Pool are ideal for large and public pools, while brands like Araz Sanat and DamaTajhiz are considered economical and high-quality options for residential pools. Choosing the right sand filter not only extends equipment lifespan but also improves water quality and enhances the swimming experience.

Technical and Professional Tips for Buying a Sand Filter

Selecting and purchasing the right sand filter requires careful evaluation of technical and operational parameters to ensure optimal performance of the water filtration system. As one of the key components in pre-treatment processes, suspended solids removal, and water clarification, sand filters play a vital role in industries, swimming pools, and irrigation systems. Below are the comprehensive technical and professional points that should be considered before purchasing a sand filter:

1. Capacity and Design Flow Rate

The capacity of the sand filter must match the inlet and outlet flow rate of the system. Flow rate is calculated in liters per second or cubic meters per hour and must be equal to or greater than the pump capacity. For accurate calculation, use the following formula:

 Q = A * v

Where Q is the flow rate (m³/h), A is the filter cross-sectional area (m²), and v is the linear water velocity (typically between 10 and 50 m/h depending on filter type). For swimming pools, the recommended linear velocity is 20 m/h. Selecting a filter with insufficient capacity results in pressure drop and reduced filtration efficiency.

2. Body Material and Structural Strength

The material of the sand filter body (galvanized steel, stainless steel, or FRP) directly affects its durability and resistance to corrosion and environmental conditions:

Galvanized steel: Suitable for environments with moderate humidity, but requires a three-layer epoxy coating with a minimum thickness of 250 microns to prevent corrosion.

Stainless steel: Ideal for acidic conditions or saline water, but comes at a higher cost.

FRP (Fiber-Reinforced Plastic): Lightweight, corrosion-resistant, and suitable for working pressures up to 150 psi, but sensitive to severe impacts.

The body thickness must also be selected based on operating pressure (2 to 6 bar) and filter dimensions to prevent cracking or deformation.

3. Type of Filtration Media

The filter media (silica, anthracite, or multimedia) significantly affects particle separation efficiency:

Silica: The most common option with grain sizes from 0.5 to 2 mm, suitable for removing particles down to 50 microns.

Anthracite: With coarser grains, used for pre-treatment of highly turbid water.

Multimedia: A combination of silica and anthracite in different layers, offering higher efficiency in removing finer particles (down to 10 microns).

Proper layering (20% coarse gravel at the bottom, 60% medium silica, and 20% fine silica) and sufficient bed depth (minimum 1 meter) are essential to ensure optimal expansion during backwash.

4. Backwash System and Valves

The sand filter must be equipped with an effective backwash system to remove contaminants from the media bed. A multiport (6-way) valve with settings for filtration, backwash, rinse, and waste is essential. A pressure gauge and nozzle manifold should also be installed to identify pressure drop in time (a drop greater than 0.5 bar indicates the need for backwashing). The backwash flow rate must be at least 1.5 times the normal operating flow.

5. Dimensions and Installation

Filter dimensions (diameter and height) must be compatible with the available installation space and accessibility. Vertical filters are suitable for limited spaces, while horizontal filters are used for higher capacities. Installation should be carried out by a specialist to ensure correct silica layering, sealing, and piping. The installation area must be level and properly drained to prevent leakage or excessive stress.

6. Quality Standards and Warranty

The sand filter must be manufactured in accordance with ISO 9001 and NSF/ANSI 61 standards. The use of high-purity silica (over 98%) with uniform grain size (tested using standard sieves) is essential. A minimum one-year warranty and technical support from the manufacturer are indicators of product quality.

DamaTajhiz; The Best Prices and Reputable Brands of HVAC Systems and Building Facilities in the Middle East (Since 2004)

When Should Sand in Sand Filters Be Replaced?

According to engineers, the silica used in sand filters should last under normal conditions for 5 to 10 years. However, observations show that sometimes filters continue to operate for over 10 years without sand replacement, but they do not perform as efficiently as they should.
On the surface of sand filters, the sand used is quite coarse. This roughness is what allows the sand to filter suspended particles in the water. Over time, as the abrasiveness of these sands decreases, the filter's efficiency declines, meaning your system has to work harder to maintain the same performance.
Findings indicate that standard silica after 5 years of continuous use can no longer fully capture contaminants, and the water does not become completely clear during backwashing. As a result, the filtration cycle shortens, backwashing is required more frequently, and for this type of silica, sand replacement is recommended once a year (depending on the type of pool and its usage).

Sand filters are used in water treatment processes for both industrial and domestic applications. They are responsible for removing suspended particles (usually up to 50 microns in diameter) from circulating water by passing it through a bed of graded sand, providing clear and purified water as a pre-treatment. Sand filters do not remove or absorb other chemical substances in the water. Generally, these filters are used for pool water, wastewater treatment, and domestic water purification systems.

Prepared and compiled by the Engineering Department of Damat Tajhiz Pool, Sauna, and Jacuzzi Equipment

Dear User:

1. We sincerely thank you for the trust you place in the technical opinions of Damat Tajhiz sales experts. It should be noted that the final determination and selection of a product brand are usually made by the buyer based on reputation, brand strength, services, and product price. However, when it comes to sand filters, most users and buyers choose popular brands like Damat Tajhiz due to their quality, price, and after-sales service.
   
   
2. If, after reviewing the above information, you have further questions regarding the purchase of any sand filter you need, you can contact Damat Tajhiz via extensions 124-125 and consult with the sales experts in the Pool, Sauna, and Jacuzzi Equipment department to get advice and ask your questions.

You can order any HVAC and MEP products, as well as pool and jacuuzi equipment, including different types of air washers, cooling towers, air handling units, chillers, industrial evaporative coolers, air curtains, burners, cast-iron or steel boilers, heat exchangers, gas heaters, unit heaters, circulation pumps, sand filters, water and fuel storage tanks, and more, from countries such as the UAE, Armenia, Tajikistan, Georgia, Azerbaijan, Turkey, Oman, Pakistan, Turkmenistan, Afghanistan, Kuwait, Bahrain, Qatar, Iraq, and others across Asia, the Middle East, and Europe, and have them delivered to your city (Manama, Baghdad, Karachi, Dubai, Sharjah, Muscat, Riyadh, Abu Dhabi, Kuwait City, Jeddah, Sana'a, and Doha Amman, Sulaimaniyah, Sofia, Kirkuk, Islamabad, Mosul, Erbil, Dushanbe, Aleppo, Damascus, Baku, Beirut, and Kabul) in the shortest possible time. So, contact us by phone call or WhatsApp message through the number: +98-930-288-0251.

"Knowledge Fuels Better Choices"

Registered Trademark and Stewardship Business Licenses Issued by the Union of Virtual Business Association and the HVAC Equipment Industry.

DamaTajhiz HVAC Participation at International HVAC and Construction Facilities Exhibitions Demonstrates its Global Reach and Commitment to the Industry.

We Look Forward to Your Call and the Opportunity to Meet You

SHARE THIS CONTENT TO SPREAD THE KNOWLEDGE