Water Heaters

Advantages and Disadvantages of Indirect Water Heater

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All of us know that a water heater is an important tool utilized for delivering hot water in a home, yet not a lot of people recognize their different types and the benefits and drawbacks associated with them. Popular types include tankless, power-vented gas, direct-fired storage electric heaters or thermal fluid heaters. Let’s take a look at the pros and cons of the indirect type.

Indirect water heaters are usually used for providing domestic hot water to a group of buildings that are not closely spaced or where individual temperature control is required. They can also be utilized in situations where there is no space available on the property to accommodate an immediate gas storage heater, an emergency firing system, or where the water heater is the only heating source.

Indirect heaters are composed of two tanks-one that heats up to store hot water and another that holds cold water. The storage tank contains a heat exchanger through which heat transfer between the gas or electric burner and cold water occurs indirectly. While there are several benefits associated with this type of heater, there are also some drawbacks.

Advantages of indirect heater:

Reduced cost.

Since they are more efficient than direct-fired storage units, indirect heaters often reduce energy costs associated with domestic hot water heating.

Reduced risk of ignition.

In comparison to direct-fired storage heaters, indirect water heaters carry a reduced risk of ignition from escaping gas, according to the U.S. Fire Administration’s National Fire Protection Association. Water is a much better natural medium for conveying combustion and does not support combustion as readily as air.

Greater safety.

Since the storage tank is outside the pressure vessel of an indirect water heater, it does not require certification under UL 128 or ASME-U for operation at domestic hot water pressures up to 160 pounds per square inch (psi).

This means that indoor installation is possible without any hassles or costs associated with a UL or ASME-U listed tank and that operation at elevated temperatures are also possible.


The expected life of indirect water heaters is longer than that of direct-fired storage units since the former does not have the stress of heating and reheating water. It has a lower loss of both hot and cold water.

Disadvantages of indirect heater:

While there are many positive aspects to owning an indirect system, there are also some drawbacks that you need to take into consideration.

Inefficient heat transfer.

Since indirect water heaters rely on the walls of their storage tanks for heat-conducting, they are not as efficient at transferring heat from the gas or electric burner flame to the water inside. This means that there is a greater amount of water in the system and this can be problematic in cold climates.


Since an indirect water heater has two tanks, it cannot be installed as easily as a one-tank system. In addition, the indirect heater does not heat up hot water as quickly as a direct-fired storage heater because it depends on external walls to conduct heat from the flame to the water inside.

Inadequate mixing and temperature control:

Since the water in the cold and hot tanks is not mixed, there can be an inadequate supply of hot water or a scalding hazard if someone turns on the cold faucet. In addition, it is more troublesome to control heating rates since each tank will have its own thermostat setting.

FAQ’s: (frequently asked question)


Indirect water heaters are less common than their direct-fired peers for a reason. This type of system may cost more and not be as efficient, but it is ideal if you have limited space or want to install the heater along with other appliances in your home. Direct-fired systems will provide hot water quickly and can be used anywhere due to their compact nature, making them a better option for installation near sinks and toilets around the house.

We hope that this article has explained to you the advantages and disadvantages of an indirect water heater if you have any questions regarding an indirect heater then make sure to leave it on the comment section.

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