Water heater expansion tank
 

Good Morning. Just want everyone to know that the expansion tanks on top of your water heater seem to be a ticking time bomb. There have been two that have failed on my block in the past six months, about six years old. If the relief valve on the top of your water heater is not plumbed directly outside, not just into the drip pan, when this tank fails the relief valve opens and will flood not just your garage but if not caught fast will flood into you house. I just changed mine and found it full of water and it would have failed soon. Bought my replacement tank at Lowes on line for under $30 and it's very easy to change out.

I heard the same issue in our neighborhood. Starting to seem like the failure isn't an anomaly. Wonder if there is a recommended window for change.

Thanks for the heads up and reminder....
:thumbup:

Don

The various tank manufacturers suggest checking the air pressure at least once a year. All you need to check the pressure is a tire pressure gauge. Tank pressure should be slightly lower than your water line pressure which runs around 55-60 psi here in the villages.

We live in an older home with no expansion tank. Our water pressure "floats" at whatever the water supply pressure is. If water in the gas water heater expands, it simply expands back into the supply line unless I have closed the main shutoff valve in the garage.

Are newer homes plumbed with a check valve in the water supply line so that water can no longer back up into the main?

I never had expansion tanks on water heaters up north so I don't know much about them. I take it there is not suppose to be any water in that tank. So if water goes into this expansion tank the water heater will release all forty gallons? How do I check this out to make sure mine is okay. By just looking, it appears to me the expansion tank is just screwed on. What is evolved in replacing it?

I don't think your water system can expand back into the water main, even if you have an older home. If you don't have an expansion tank, the pressure in the water heater can exceed 100 PSI and cause the emergency relief valve on the tank to open and spew out hot water. Or worse, the relief valve can be stuck and fail to open and the water heater can leak or explode. High pressure can also damage your faucets and other plumbing fixtures. I would suggest that you consider installing an expansion tank.

The expansion tank is designed to be about one half full of water and one half full of air. The water and air are separated by a diaphram that is flexible. The installer pumps air into the expansion tank to a pressure of about 60 PSI. Since air easily expands when the temperature and/or pressure increases, it works to maintain a constant water pressure in your house, by providing an air cushion. Without an expansion tank, your water pressure can greatly increase when the water heater heats up because water does not expand very much in a closed system. This is especially true if you have no plumbing leaks and all of your fixtures are turned off. The air pressure in the expansion tank can be checked just like the tire pressure on your car. And, you can increase or decrease the air pressure with a simple bicycle pump.

My home was built in 2013. Should I be concerned?

No, I wouldn't be concerned as long as the water pressure in your house does not seem to be excessive when you turn on a faucet. If you suspect high pressure, a simple way to see if the pressure relief valve on your water heater has been tripping, is to place a small plastic cup under the discharge pipe for a few days to see if any water has been released. When the water pressure get high enough, the relief valve will open for a few seconds to relieve the pressure. But, if the expansion tank is working, this should never happen.

What you described is not normal operation of the relief valve. The relief valve is designed to only open when the pressure exceeds 100 PSI, and to automatically close when the pressure goes down. So, usually it will only release a small amount of water, maybe a cup or so. It sounds like the relief valve was defective because it didn't close properly. It would only stay open if the water pressure into your house was higher than 100 PSI. So, even if the expansion tank is full of water, your house should not get flooded unless there is a leak. Just my opinion.

Here’s a good read, not only explaining why an expansion tank is needed and what it does but also how to test it and replace it if necessary.

Testing and Replacing a Hot Water Expansion Tank

The water pressure in my house seems normal. So I'm not going to start messing with something that's not broke . Thanks for the info.

When you replace an old water heater, some plumbers will cut corners by not installing an expansion tank if you didn't have one there before. In my opinion, that is a mistake, and you should pay the extra charge to get one installed.

My understanding is the the expansion tank is to prevent water hammer and burst pipes. They act as shock absorbers only and are not really necessary.