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  • Writer's pictureRob Mitchell

Do I have a Steam or a Hydronic boiler?

Updated: Jan 9

Today, there are many different types of heating systems that can heat your home. One of the most traditional systems is a boiler system which uses water to create heat for your home. There are two types of boiler systems, steam or hydronic (hot water). Both provide clean, dust free heat.

Both of these types of boilers can use natural gas, electricity, or oil for power. In addition, they both use hot water as their main heat source. How they create heat, however, is what sets them apart.

A steam boiler heats water to a boiling point (212˚) in order to create steam. The inherent pressure behind the steam forces it to move through a network of pipes, in most cases, to freestanding cast-iron radiators around your home. When the steam condenses it travels back to the boiler and is reheated.


A hydronic boiler, on the other hand, heats water just until it’s hot enough (160˚ - 180˚). It then circulates it through a pump, and sends the water flowing into your piping. The water radiates the heat in your rooms through a heat emitter, such as a steel or fin tubed baseboard, and then the water returns to the boiler to be reheated.

Hydronic boilers don’t only work with baseboards – you can also use them in radiant floor heating systems or to heat towel rails, swimming pools, and driveways to melt snow. These modern comforts can be individually adjusted to achieve the perfect temperature in every application.

Understanding the type of heating system you have can be helpful when scheduling maintenance services. Here are a few tips to help you determine if you have a steam or a hydronic boiler.

If you see only one pipe coming from your radiator, that means you have a one-pipe system, and it is definitely steam. The steam comes through the pipe, the heat is dispersed, the steam condenses in the radiator, and the water returns through the same pipe to the boiler.

Two pipes coming from the radiator means it could be either a hydronic system or a steam system.

If you sometimes hear a high-pitched whistle coming from your radiator, you most likely have a steam heating system.

Boiler sight glass

Do you have a “sight glass”? You will have to go to the basement and look at the boiler for this part. A sight glass is a transparent glass cylinder that is about 12 inches tall, filled partly with water to indicate the level of liquid contained within the system. Steam heating systems should always have a sight glass attached vertically to the outside of the boiler.

If a circulating pump is attached to your boiler, it usually means you have a hydronic system. Circulating pumps come in all sorts of vibrant colors.

If you have hydronic heating, you should also have an expansion tank near the boiler. The expansion tank protects the hydronic system from building up excessive pressure.

Both steam boilers and hydronic boilers offer energy efficiency, but in different ways. A steam boiler uses more energy to boil the water, but uses less energy during the transfer of heat. A hydronic boiler uses less energy to create hot water, but more energy during the transfer of heat.

Many of today’s hydronic boilers are considered more efficient than steam because they have pumps for circulation. However, you can still find some steam boilers that are just as (or more) efficient than hydronic. Each boiler’s efficiency depends on its manufacturer, heat source, size, and more.

Because these systems are both boilers, they tend to cost around the same price to install. When you’re trying to decide between a steam boiler and a hydronic boiler, you’ll need to consider the cost of your fuel (gas, electricity, oil, etc.), the cost of the system, possible tax credits, and other details.

We hope this helped you learn more about your heating system. No matter what type of heating system you have, we can help you maintain it.

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