What is an Expansion Tank and Why Do I Need One? - Service Mark Solutions

What is an Expansion Tank and Why Do I Need One?

One wasn’t attached to your old hot water heater tank, so you may not even know what a (thermal) expansion tank is, let alone why you probably need one today. Truth be told, in the past, they were not as necessary as they are today.

An expansion tank looks like a mini tank or boiler, and typically sits on top of, or adjacent to, the water heater. They come in many different sizes, depending on your water pressure, the size (in gallons) of the actual water heater, and the temperature the water is heated to. But why are these different factors so important?

As water is heated, it expands and its’ pressure, in the tank vessel, will increase if there’s no room for the thermal expansion. The old domestic hot water heater plumbing systems were designed so that the expanding water in heaters would push some water back outside the house – into the public water main, which would absorb the pressure. But, because township water companies and some government agencies do not allow an unpredictable backflow of water back into their system, this release mechanism doesn’t work anymore.

Today’s plumbing systems, including your home’s hot water heater unit, utilize controls and other devices, such as check valves, (placed in the cold-water feed piping) for efficiency and comfort, often creating what is called a “closed system”. The purpose of these one-way valves is to prevent water from flowing backwards out of the house through the supply piping, which prevents a possible contamination from getting into the public water supply.

Frozen copper pipe that has cracked

The inherent problem with check valves placed in the system is that the water pressure builds up in this closed system until someone opens a valve. If water pressure gets high enough for a long enough time, there’s a high risk of damage to plumbing fixtures, water supply piping and even the water heater itself.

Why should your water heater have an expansion tank installed?

All water heaters, regardless of whether they use heating oil, natural gas or propane or even electricity, can suffer the negative effects of thermal expansion as the cold water coming into the tank turns to hot heated water, increasing the overall water volume via expansion and increasing pressure inside the tank. The increase in volume and pressure must be relieved for overall safety.

Here’s where the expansion tank comes into play: when both sized correctly and installed correctly, it absorbs this “extra” water into a bladder, located inside the expansion tank, and minimizes excess pressure in the water heater unit.

If your domestic hot water heating system does not have a working thermal expansion tank, swings in water pressure can take years off your tank’s integrity cause leaking or bursting of your water heater tank because the glass lining of the water heater and other plumbing fixtures and components get stressed and damaged.

An expansion tank helps maintain a minimal pressure increase during heated water expansion, helps reduce water hammer, and helps protect the plumbing system from stress, and, of course, leads to a longer tank life. To do so, it must be properly located, sized, and piped into the overall system. Also, to help avoid and prevent premature failures, your expansion tank should be checked annually.

Our HVAC (Heating – Ventilation – Air Conditioning) technicians will make sure each expansion tank is correctly installed, and maintained, to prevent water hammer, high water bills and unnecessary wear on the water heater and plumbing fixtures.

If your hot water heater tank has a check valve or pressure-regulating valve on your water main, then you should immediately consider installing a thermal expansion tank.

At ServiceMark Heating Cooling & Plumbing, our fully trained team of exceptional HVAC installers, technicians and support staff are ready 24/7 to help make your home not only comfortable but safe as well! We pride ourselves on delivering HVAC solutions that meet your needs for today and years to come.

Please contact us today for further information and to schedule an appointment for all your HVAC repairs, maintenance and installation in Exton and King of Prussia PA and Wilmington DE.