Hot water on demand is one of the modern basics of our homes and it’s not until something goes wrong and we’re left under a cold shower that we begin to question how the system really works and what protective measures we should take.

Standard water heater tanks can put your plumbing under pressure and strain due to normal thermal expansion that occurs during the water heating process. For this reason, modern homes that are in a closed water system need a safety device known as the thermal expansion tank to help alleviate the pressure in the system and prevent potential damage.

Here are the most important facts about the role of the expansion tank in protecting your hot water system.

Basic facts

When water is heated, it expands and when this happens in your plumbing system, this extra water needs to be released somewhere. This is where the expansion tank comes in. It serves as a receptacle for the overflowing water by taking it in. It absorbs both excess water produced by the water heater tank and the fluctuations in incoming water supply pressure.

In essence, every time the water heater heats water, an excess amount of water is created due to thermal expansion and it can create added pressure in the plumbing system. This can cause damage to the water heater tank itself, as well as the plumbing fixtures and water pipes.

How does it work?

Thermal expansion tanks have a special rubber balloon or a bladder inside with an air cushion on one side whereas the other side is connected to the piping system. When water is heated inside the hot water tank and starts expanding, excess water flows into the expansion tank and presses the bladder compressing the air cushion, which then allows all the excess water to come in. Next time someone opens a faucet, the compressed air presses the bladder again and pushes the water in the other direction back into the plumbing system.

This device is usually located next to the water heater tank, on the cold water supply line and it’s finely sized and tuned so that it can correctly optimize water pressure. When getting a new expansion tank, you need to know that there are different sizes depending on the water pressure, amount of heated water and its temperature.

Why install an expansion tank?

In older homes that have an open system, expanding water is pushed back directly into the city water supply and there’s rarely any problem. However, most homes today have a closed water heater installation where there’s a one-way valve or a backflow valve that reduces the pressure. The expanding water cannot be sent back into the public water system, but it stays within its closed circuit.

When water is heated within a closed system, pressure builds up as water is expanding. It can go well beyond a normal working pressure, exceeding 150 psi. The check valve opens and reduces the pressure from the water heater. A system that doesn’t have an expansion tank will have large swings in water pressure, potential damage to the glass lining of the water heater and other issues with plumbing fixtures and plumbing components.

All of these aspects can play a potential part in the entire plumbing system as water is basically trapped within a closed system until the valve is opened. So, installing an expansion tank is a safety measure that helps maintain minimal pressure and protect the plumbing system from additional strain.

Having a high quality expansion tank correctly installed to your hot water system will help maintain its proper functioning and prolong its lifespan. Without it or with incorrect installation, you are at risk of high water bills, water hammer, excessive strain and wear on your water heater and the entire plumbing system. If you’re having problems, then you can contact a boiler service for repairs.