Massachusetts Home Buyer Guide

Most prospective Massachusetts home buyers assume the tank near a home's heating system is a hot water heater, producing hot water for showers, washing clothes, or cleaning dishes. Most of the time, that's correct, but not always.

An indirect hot water tank is one alternative to a traditional hot water heater. An indirect hot water tank, also known as an indirect water heater, is a water heating system that uses an external heat source, such as a boiler or a solar thermal system, to heat water. It is called "indirect" because the heat source does not directly heat the water inside the tank but transfers heat through a heat exchanger.

Indirect hot water tanks are typically well-insulated to minimize heat loss, and they can be integrated with various heat sources, including boilers fueled by natural gas, oil, or propane, as well as solar thermal systems, heat pumps, or geothermal heat sources. 

Here's how an indirect hot water tank typically works:

(1). Heat Source: The primary heat source, such as a boiler or a solar thermal system, generates hot water or, in some cases, steam or a water-glycol mixture.

(2). Heat Exchanger: The hot water from the heat source flows through a coil or a heat exchanger inside the indirect hot water tank. The heat exchanger is usually made of copper or stainless steel and is immersed in the tank.

(3). Heat Transfer: As the hot water passes through the heat exchanger, it transfers its heat to the water inside the tank without coming into direct contact with it. The heat exchanger efficiently transfers the heat from the primary source to the water.

(4). Hot Water Storage: The heated water in the tank is stored for later use. The tank acts as a reservoir, ensuring a steady hot water supply.

(5). Domestic Hot Water Supply: When you turn on a faucet or a shower, cold water from the main supply enters the tank and flows through a separate pipe inside the heat exchanger. The cold water absorbs the heat from the heat exchanger and exits the tank as hot water, ready for use.

The main advantage of an indirect hot water tank is its efficiency. If used with a high-efficiency boiler and well-insulated tank, an indirect water heater can be the least expensive means of providing hot water in your home. 

Related: Pre-offer Home Inspections: What Massachusetts Homebuyers Should Know

Indirect water heaters are more efficient than other types of domestic water heaters for most homes, even though they require a storage tank. The energy stored by the water tank allows the boiler to turn off and on less often, which saves energy. Also, indirect hot water tanks do not have a vent, so they do not lose heat through an exhaust pipe.

The heat exchanger also allows for quick and efficient heat transfer, ensuring a rapid hot water supply. Since the heat source doesn't come into direct contact with the water, there is no risk of contamination or scaling. Traditional hot water heaters typically heat the water directly using natural gas, propane, or electricity.

A home buyer or new homeowner will want to consider the following concerning indirect hot water tanks:

• The size of the home and the number of people who live there will affect the tank size needed.

• The type of boiler or furnace present will affect the compatibility of the tank.

• The insulation of the tank will affect its efficiency.

• The warranty offered by the manufacturer is an important consideration.

Besides efficiency, indirect hot water tanks save consumers money in other ways. Indirect hot water heaters are more durable because of their thicker materials than traditional tank water heaters, making them more damage-resistant and longer lasting.

Indirect water heaters are some of the least complicated domestic water heater systems, meaning there are fewer parts and a more straightforward product requiring less maintenance. There's also no burner in the tank which minimizes sediment buildup.