Calculate Pool Sand Filter Capacity

A sand filter is an essential piece of equipment in swimming pools and jacuzzis whose primary task is physical water purification. By removing suspended particles, impurities, and contaminants, sand filters enhance water quality and create a healthy and hygienic environment for swimmers. Without a sand filter, the water of the swimming pool or jacuzzi becomes contaminated quickly, making it potentially dangerous and unhealthy. Therefore, selecting and calculating the appropriate capacity of the sand filter is one of the most important steps in pool and jacuzzi design and maintenance.

sand filter capacity

Sand Filter Capacity Calculation

Sand filter capacity is a critical factor, because among the essential equipment in the pool and jacuzzi industry is the pool sand filter, which plays a crucial role in maintaining users' health and extending the service life of the water treatment system. Physical filtration by the sand filter removes suspended particles and impurities, making the water remain clear and clean. Furthermore, it reduces chemical consumption, making pool equipment experience less wear and last longer.
All types of pools require a sand filter, whether private or public, indoor or outdoor. Selecting the appropriate capacity depends on the pool size, water turnover rate, water flow rate, number of users, etc. So, in the following, you will study steps towards calculating the sand filter capacity for your pool or jacuzzi.

Calculating the Pool or Jacuzzi Volume

The first step towards sand filter capacity calculation is the accurate calculation of the pool or jacuzzi water volume. Water volume is the main criterion for determining the filter capacity and the required flow rate, and it is calculated according to the pool's geometry.

Calculating the Volume of Rectangular Pools or Jacuzzis

Calculating the volume of water in rectangular pools or jacuzzis is as easy as pie. Here is the formula for the volume of all rectangular cubes:

$Volume of water (m³) = Length \times Width \times Depth$

V = L \times W \times H

Example: If the pool is 10 meters long, 5 meters wide, and has an average depth of 1.5 meters:

$Volume of water (m³) = 10\times5\times1.5=75 m^3$

The solution: Multiply length by width by depth: 10 × 5 = 50; 50 × 1.5 = 75 → Volume = 75 m³.

Circular Pool and Jacuzzi Capacity Calculation

The capacity calculation for circular Pools, for a sand filter capacity calculation, follows the formula of volume. So:

$Radius^2 × Depth$

V = pi \times r^2 \times h

Example: For a circular jacuzzi with radius 2 meters and depth 1.2 meters:

$3.14 \times 2^2 \times 1.2 \approx 15.1 (m³)$

The solution: Compute radius squared: 2^2 = 4. Multiply by π (approx. 3.14): 3.14 × 4 = 12.56. Multiply by depth 1.2: 12.56 × 1.2 = 15.072 ≈ 15.1 m³

Moreover, if the pool or jacuzzi doesn't have a specific simple shape, you can divide its parts into simple shapes and then use the appropriate formula for each part, and then sum all.

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Determining the Water Turnover Rate

Water turnover rate refers to how many times the entire pool water must pass through the sand filter during a day. This rate depends on the pool type, coverage, number of users, and environmental conditions.

Standards:

Indoor residential pool: full water turnover every 6 hours (4 times per day)
Private outdoor pool: at least 3 to 4 times per day
Public or club pool: due to a larger number of users, 6 to 8 times per day is recommended

Determining the appropriate turnover rate ensures the pool water remains clear and hygienic and prevents unnecessary stress on the filter.

Calculating the Pool Flow Rate

Flow rate is the amount of water passing through the filter per unit time. It is essential to consider the pool flow rate when selecting a sand filter.

Flow Rate (m³/h) = Pool Volume (m³) ÷ Turnover Time (h)

Pool Volume (m³): The total volume of the swimming pool in cubic meters.
Turnover Time (h): The time required for the entire pool water to pass through the filtration system once.

Example: If the pool volume is 120 m³ and the water must turn over every 6 hours:

Flow Rate = 120 ÷ 6 = 20 m³/h

The solution: Divide total volume by turnover time: 120 m³ ÷ 6 h = 20 m³/h → Flow rate = 20 cubic meters per hour.

Note: Filter flow rate and turnover time are inversely related. The shorter the turnover time, the higher the flow rate

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Selecting the Diameter and Height of the Pool Sand Filter

When selecting a sand filter, the filter diameter and height play an important role and must match the water flow rate and required capacity. The sand filter size calculator concerns:

Metal sand filter: It is recommended that for every 10 sq. ft (0.93 m²) of filter area, a flow of 5 gallons (18.93 l) (≈20 liters) per minute is used.
FRP (fiberglass/polyethylene) sand filter: For every 10 sq. ft, a flow of 15 to 20 gallons (75.71 l) (≈60 to 75 liters) per minute is suggested.
Filter height: It is usually considered as 1.2 times the filter diameter.

Note: FRP filters can withstand temperatures up to only 40 °C, and for jacuzzis with higher temperatures, more resistant options should be considered.

Quick Pool Sand Calculator

A sand filter is one of the most essential components in swimming pools and Jacuzzis, responsible for the physical purification of water. By removing suspended particles, impurities, and contaminants, it ensures clean and safe water for users. Calculating the correct capacity of a sand filter is critical and depends on the pool’s volume, flow rate, number of users, and water temperature.
To determine the right filter size, the pool volume must first be calculated based on its shape (rectangular or circular). Then, the turnover rate (the number of times water circulates through the filter daily) is established according to pool type: 4 times per day for private indoor pools, 3–4 times for outdoor private pools, and 6–8 times for public pools. Based on this, the flow rate is calculated by dividing the total water volume by the turnover period.
Finally, the diameter and height of the sand filter are selected according to the required flow rate. Metal filters and FRP filters have different flow capacity standards, and the filter height is usually 1.2 times its diameter. Choosing the right filter ensures better water quality, reduces chemical usage, and prolongs the life of pool equipment.

FAQs about Sand Pool Filter Capacity Calculation

Hoping you now know everything about how it is possible to easily select a sand filter capacity, we invite you to study frequently asked questions about this subject and DamaTajhiz experts' answers to them.

How much Sand Goes in a Pool Filter?

There’s no one-size-fits-all answer, but typically:

A 16-inch sand filter requires around 100 lbs of sand.

For each inch above 16", add approximately:

+25 lbs per inch up to 20"
+50 lbs for every 2 inches (5.08 cm) between 20" and 24"
+50 lbs for every 3 inches (7.62 cm) between 24" and 27"
Above 27", add 150–200 lbs for every 3 inches (7.62 cm)

For instance, a 24" filter typically needs about 300 lbs of sand

How to Calculate Volume of Sand Filter?

All this article was about how to calculate volume of sand filter. While sources more often cover pool volume, determining the required sand for a filter involves:

Studying the user manual provided by the manufacturer for the specified sand amount is the most reliable method
Use general sizing charts based on tank diameter, as shown above.
Some advanced tools allow you to input the filter’s internal volume and type of media to get a precise result

How Long Does Sand Last in a Pool Filter?

Sand typically lasts 5 to 7 years before losing effectiveness due to wear of the media edges

The Final Note

You just comprehended how easy sand filter capacity calculation is. Now that you know every tip for calculating the volume and capacity of a sand filter for your pool, you can easily decide and select one. Anyway, if you have any questions or want further guidance, you can get in touch with DamaTajhiz HVAC & MEP experts with a phone call or WhatsApp message through the number: +98-930-288-0251.

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