Coiled Tank

If you plan to buy a coil water heater tank for domestic hot water but are unsure about the right size or brand, this guide explains how to choose the proper capacity and includes a price list.

Professional Guide to Selecting and Pricing Coiled Tanks

A coiled tank (or coil-type storage water heater) consists of a galvanized cylindrical reservoir combined with several rows of copper tubes or coils. These coiled water tanks are manufactured in two configurations: horizontal and vertical (standing), with various capacities ranging from 300 to 6000 liters.
In coiled tanks, cold water is stored inside the galvanized cylinder and is heated through contact with the hot water or steam flowing through the copper coil connected to the boiler. Therefore, the coil-type water heater tank is widely used to supply domestic hot water in buildings and various industries.
The hot water coil tank includes two inlets and two outlets: one set for the cylindrical reservoir and the other for the copper coils. Due to the high heat exchange surface of the copper coils, these tanks offer higher efficiency and faster heating performance compared to double-walled tanks.
Coiled tanks are highly efficient, easy to clean and maintain, can be installed either horizontally or vertically (depending on the application), and are durable, making them suitable for use in heating plant rooms and mechanical systems.
The main difference between a coiled tank and a double-walled tank lies in their internal structure. In double-walled tanks, two cylindrical containers are placed one inside the other, whereas a coil-type water tank uses copper tubes inside a single tank to transfer heat.

Types of Coiled Water Tanks

Coil water heater tanks are categorized based on their installation position, number of coils, tank material, and type of working fluid, as follows:

Types of Coil Hot Water Tanks Based on Installation Position

- Horizontal coil water tank
- Vertical (standing) coil water tank

Types of Coil Hot Water Tanks Based on Number of Coils

- Single-coil water heater tank
- Double-coil water heater tank

Types of Coil Water Heater Tanks Based on Tank Material

- Coiled tank made of hot-dip galvanized steel sheet
- Coil tank made of black carbon steel sheet

Types of Coil Hot Water Tanks Based on Working Fluid

- Water-to-water coiled tank
- Steam-to-water coil tank

Differences Between Horizontal and Vertical Coil Water Tanks

In horizontal coiled tanks, the water cylinder is positioned horizontally (laid down) and can accommodate larger-sized coils. Therefore, using this type of tank is not suitable in areas with limited space.
Vertical (standing) coil tanks, on the other hand, feature an upright cylinder and are preferred in cases where floor space is limited. However, since larger coils cannot be installed inside vertical tanks, they have lower heating power and capacity compared to horizontal coiled tanks.

Main Components of a Coil Water Heater Tank

If you intend to purchase a coil-type water heater tank, you should know that this tank consists of components such as the main tank, coil, safety valve (temperature and pressure), supports, and drain valve, which are described as follows.

Tank

The most essential component of a coil-type hot water tank is the cylindrical tank, usually made of hot-dip galvanized steel that is resistant to pressure, corrosion, and scaling. The primary function of this tank is to store the cold water volume and the copper coils of the tank.

Coil

Another main component of a coil-type water heater tank is the coil, which consists of multiple U-shaped copper tubes with appropriate thickness and diameter, arranged neatly and systematically together.

The coils in coil-type tanks are responsible for transferring heat from the hot water received from the boiler to the cold water inside the tank.

Safety Valve (Temperature and Pressure)

In general, the function of safety valves is to control, reduce, and prevent excessive pressure in closed equipment and tanks, such as a coiled tank, ensuring stable pressure of the working fluid.

Drain Valve

At the bottom of the coil tank, there is a component called the drain valve, which is used for complete drainage of the tank during potential maintenance or repair operations.

Applications of Vertical and Horizontal Coil Water Tanks

Coiled tanks are widely used due to their numerous advantages.

The advantages and applications of coil water heater tanks include:

• Residential projects, offices, and commercial buildings
• Factories, workshops, and industrial facilities
• Worker camps (with central heating systems)
• Hotels and schools
• Swimming pools

Advantages of Coiled Water Heater Tanks

As a practical HVAC equipment for supplying domestic hot water, coil water tanks offer the following benefits:

1. Durable and strong body, resistant to environmental conditions, with long service life
2. Higher operational efficiency due to the presence of the coil (or heat exchanger) inside
3. Ease of maintenance due to single-wall design (in case of leaks)
4. Faster water heating inside the tank due to the use of copper heating coils with sufficient heat transfer surfaces

Note: The body of coil tanks is usually made of hot-dip galvanized steel. Therefore, if black steel sheets are used, the internal surface is fully coated with epoxy paint to prevent rust and oxidation.

Damatajhiz: Guide for Selecting and Purchasing HVAC and Mechanical Equipment (since 2004)

Technical Points for Choosing a Coil Water Heater Tank

When selecting a coil-type water heater tank, attention should be paid to the following important technical points:

• For coiled tanks with a capacity greater than 1500 liters (upon customer request), a circular manhole, known as a "manhole cover," is provided for internal access and potential maintenance, such as applying epoxy inside the tank.
• The design temperature considered for the coils is 350°F.
• Each coil water heater tank must have appropriate supports made of structural steel for stability and proper installation.
• Necessary bushings for hot water outlet, water inlet, drainage, thermometer, thermocouple, thermostatic valve, pressure gauge, and safety valve should be welded to the coiled tank.
• After cleaning the internal surface of the tank, at least two layers of special epoxy paint are applied. After anti-corrosion treatment of the external surface, oil-based paint is used.
• The copper coil must be manufactured according to ASME and BS standards.
• For ease of handling, each tank is equipped with two dedicated hook points for lifting and transportation.
• For coil manufacturing, copper tubes with diameters of 3/4 inch or 7/8 inch are usually used.
• The end cap of the coiled tank must be made of alloy steel and must be flanged.
• If the lowest part of the coil in a horizontal coil tank is above the boiler collector level, domestic hot water supply can be achieved without using a circulation pump.

How a Coil Water Heater Tank Works

The coil water heater tank is a vessel designed to provide and store the domestic and sanitary hot water required in buildings and industrial facilities. These tanks also function as a type of coil or tubular heat exchanger, transferring heat from the hot water inside the coil to the cold water in the tank, thereby heating the tank water and supplying the needed hot water.
The coiled tank provides domestic and sanitary hot water indirectly.
The operation of a coiled tank is such that hot water or steam from the boiler enters the copper tubes (coil) inside the tank. As the flow passes through, the temperature of the coils rises and transfers its heat to the cold water inside the tank. In this way, the hot water required for the project is provided without mixing boiler water with the potable water.

Practical Note: In projects where the boiler room is located on the roof of the building, to prevent air locks in the hot water outlet of vertical coiled tanks, it is recommended to install the hot water outlet bushing on the cylinder slightly below the weld of the top end cap, instead of using the top end cap itself Additionally, a branch from the top of the end cap should connect to a diaphragm tank designed to collect excess air from the coil water heater tank, as the top safety valve of coil tanks may get clogged over time and fail to release excess air properly.

Buying a Coil Water Heater Tank

When selecting and purchasing a coiled tank as one type of hot water tank, it is crucial to pay attention to two parameters: tank volume and coil heat exchange surface area.
To purchase a coil water heater tank, you must first determine the desired capacity and type of tank (vertical or horizontal).
At Damatajhiz, technical information about various coiled tanks from reputable brands with original warranties is provided to ensure an optimal and informed purchase experience.

Important Note: When selecting and ordering a coil tank, besides capacity, coil heat surface, thickness, and tank material, special attention must be given to the diameter and length of the tank for passage through the boiler room door and proper installation at the intended location. Once a coiled tank is manufactured, it cannot be returned.

DamaTajhiz; Guide to Selection and Pricing of HVAC and Building Facilities Equipment (Since 2004)

Coiled Tank Price

The main factors determining the price of a coiled tank are tank capacity, type and number of coils, and tank material, which are key elements in the pricing of a coil water heater.

All prices for vertical and horizontal coil tanks provided by Damatajhiz are up-to-date, including special discounts for consumers. Therefore, we guarantee that these prices are the best and most competitive for high-quality coiled tanks with original warranty.

Updated Coiled Tank Price List

Dear users, in this section you can view the latest Coiled Tank Price List for November 2025 from top-selling and trusted brands such as Araz Sanat, Khazar Boiler, and Damatajhiz, and enjoy special discounted prices.
The following table presents the technical specifications and prices of different horizontal and vertical coiled tanks with various capacities from each brand.
Before purchasing a coil-type tank, we recommend contacting the technical experts at Damatajhiz to receive free professional consultation, verify suitable pricing, and review detailed technical specifications.
The technical table below lists various vertical and horizontal coil tanks by DamaTajhiz, Khazar Boiler, and Azar Sanat, along with their capacities and prices.

Coiled Tank Brand	Type	Coiled Tank Capacity (liters)	Price (USD)
Damatajhiz	Horizontal	300–2000	From 210 to 1033
Damatajhiz	Vertical	400–6000	From 287 to 1487
Khazar Boiler	Vertical	1000–5000	Contact for price
Araz Sanat	Vertical	2500–3000	Contact for price

Coil Water Heater Tanks Installation

A coiled tank has six inlets and outlets. Two inlets are for the boiler hot water, entering the coil from the top and exiting from the bottom. One inlet below the coil is designed for domestic water, which enters the coil after passing through a water softener.
The outlet for potable water is located at the highest point to ensure natural convection allows water supply to residents even if the pump fails.
Additionally, an air vent valve should be installed on top of the tank, on the upper end cap below the hot water outlet, to enable air release when necessary. It is recommended to pipe from this point downwards so discharged water falls safely to the ground. Another drain valve should be installed at the bottom end cap for tank emptying during replacement.
A return path for hot water in the body, usually above or in line with the coil, is necessary. This return must also include a valve and a check valve.

Note: One critical point in operating coiled tanks (vertical and horizontal) is the need for complete insulation of the tank surface to prevent excessive heat loss and avoid overheating the boiler room air.

Effect of Anti-Scaling Devices in Coiled Tanks

Water hardness causes scale formation inside the coil of coil water tanks. Scale acts as an insulator, reducing heat transfer efficiency and overall performance of the coil. In such cases, a magnetic anti-scaling device can be used.
The anti-scaling device is installed on the cold water supply line to the coiled tank, generating a magnetic field that alters the structure of calcium and magnesium carbonate particles, preventing scale formation on the coil.

DamaTajhiz: Thousands of products for thousands of projects (since 2004)

Dear User;

Thank you for trusting the technical opinions of Damatajhiz sales experts. Usually, the final choice of brand is based on experience, brand strength, services, and price by the buyer. However, for coiled tanks, most buyers prefer well-selling brands such as Damatajhiz due to their quality, price, and after-sales service.
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