What is an expansion tank, and why do you need one?

A hot water expansion tank

What is an expansion tank, and why do you need one?

What could be worse than a cold shower in the morning? Running out of hot water is an inconvenience and adding extra capacity can be tempting. When shopping at your local hardware store, it would be understandable if you thought a hot water heater expansion tank would store extra hot water for you. In fact, an expansion tank is an important safety addition to your plumbing designed to protect the integrity of your hot water heater and your property.

In newer plumbing systems with backflow prevention, heating water causes an increase in pressure in your hot water tank and pipes. Expansion tanks are designed to relieve this pressure build up, preventing your pipes and hot water tank from bursting.

Traditionally, temperature and pressure relief valves were used to help with thermal expansion, but T&P valves are no longer considered to be good enough because mineral deposit build-up often leads to T&P valve failure. This can cause off-gassing, distorted hot water tanks, or even a hot water heater explosion. Just ask the Mythbusters.

How does an expansion tank work?

Expansion tanks look very similar to propane tanks that you use to fuel your BBQ.

An Installed Expansion Tank

An Installed Expansion Tanks; image from https://en.wikipedia.org/wiki/Expansion_tank

They are separated into two compartments by a diaphragm, with the upper portion connected to the plumbing directly and the lower half filled with compressed air. When the volume of water expands due to heating, the upper compartment can push into the air filled portion, relieving the stress on the system as a whole.

You can tell if an expansion tank is working by tapping on it- it should sound full on top and hollow on the bottom. Also, the upper portion should be warm to the touch. If the entire tank is full then it is not functioning properly, and it should be serviced or replaced

What does plumbing code have to say

The International Plumbing Code (IPC), Uniform Plumbing Code (UPC) and the Standard Plumbing Code require that thermal expansion must be accounted for.

How do I know if my plumbing is suffering from overpressure

There are many clues that your plumbing may have high-pressure problems including:

  • toilets that run sporadically for no apparent reason
  • difficult to operate taps
  • strange leaks developing in the pipes

One of the telltale signs is if there is an occasional sudden rush of water when you turn a hot water tap on in your sink.

The many advantages of having a thermal expansion tank

  • Your hot water tank will last longer, saving you money
  • It will reduce the chance of leakage in your water pipes
  • Reduces stress and wear on your plumbing, making it less likely that you will need expensive repairs in the future
  • Lowers the risk of catastrophic water leaks, protecting your property from water damage
  • It’s a requirement for a full warranty on many hot water tanks

Added risks for condo units

For condo units above the first floor, having a hot water tank without a thermal expansion tank can put your home insurance policy at risk. Depending on the make and model of your water tank and the building’s history, a water leak that damages any units below you may not be covered. This is a situation we have come across in Edmonton, and we know how to fix your hot water system to restore your full house insurance.

Do you need some advice about hot water expansion tanks? Leave us a message at (587) 773-2612 and we will get back to you as soon as possible, or call (780) 231-0064 if you need to speak to someone immediately. To schedule an appointment, pick your preferred time on our online booking page.

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