Do you have a thermal expansion tank on your water heater?

[ruffdog]

In our nearby city they have been installing back flow preventers on everybody’s water service. Without an expansion tank people are having their emergency release valves on the water heater weeping. I’d say if you don’t have that problem I wouldn’t worry about it.

I've never heard of using an expansion tank for a water heater. The simple fact is that if you are on a well and do not have a check valve "after" your pressure tank you already have an expansion tank.
On city water if they are installing check valves at the house and you don't normally have a pressure tank I could see where it might be beneficial to have one.
My boiler system has an expansion tank it also has a check valve to prevent boiler water from getting back to the house water lines.

People that have your own well and have a pressure tank already have an expansion tank....the pressure tank. With city water with a back flow check valve, you now have no where for the hot water to expand to, hence the need for the small expansion tank.

 

[2manyrocks]

I don't have an expansion tank, but I added an air chamber to my water heater that stopped nuisance valve leaks. You can make one from a couple of small sections of pipe, a pipe cap, and tees. I incorporated a couple of valves in mine so I can drain any water that might collect in it. What is an Air Chamber in Plumbing? And Why They're Important. - plumbing review

 

[kenmbz]

I have two expansion tanks.
One on the oil boiler as it also provides hot water.
One off of the solar hot water.
They are needed for code, and since there is a backflow protector back to the water supply tank (well supplied).
I was told they keep the pressure stable.

 

[EddieWalker]

I've only seen one in a house here in East Texas, and that was on an older 1950s home that had been extensively remodeled. The reason I was there was because it was leaking really bad and flooding the house. I removed it and plugged the threaded fitting that it was attached to. Problem solved. I asked the homeowner if they wanted another one installed, and they said no. Lowes and Home Depot have them sitting on the shelf, so I'm guessing they sell enough of them to keep them stocked, but I just don't see them anywhere. I don't have one in my house.

 

[woody]

My daughter was having trouble with her pop off valve leaking and got my son to come over and change it but it did not help so they put a pressure gauge on it and she said the pressure was running up extremely high so they replaced the pressure regulator at the meter and it still leaked. then they came to me and I replaced the thermostat on the water heater problem solved. The man at the hardware store that was trying to help told her she needed an expansion tank and since she had never heard of one she called me I told her she has never had one before so something must have changed that is when I found the thermostat bad.

 

[ponytug]

I've had 3 water heaters installed since about 2010 by registered plumbers. Two in Virginia, one in Mississippi. There was no mention of a need for a thermal expansion tank. Then yesterday my son tells me it's code in Virginia. Reading up on thermal expansion tanks it seems they need to be checked annually and are often a point of failure due to rust.
A quick attempt at online research indicate that one of the reasons to have a thermal expansion tank is to prevent the temperature and pressure relief valves from failing.
For the last 50+ years I had thought that if the temperature and pressure relief valves started routinely leaking it was time to replace the water heater.
So my question is how important is this if you have "soft water"?

If you don't have an issue, you don't want one. They are a service item, and most home owners don't proactively replace them, and have water leaks with the ensuing damage.

In general, they are only needed if the system is sealed up by a back flow preventer or a check valve, or a water pressure regulator. If you have a hot water hydronic heating system, those need to be sealed and have to have expansion tanks.

All the best,

Peter

 

[ovrszd]

I've only seen one in a house here in East Texas, and that was on an older 1950s home that had been extensively remodeled. The reason I was there was because it was leaking really bad and flooding the house. I removed it and plugged the threaded fitting that it was attached to. Problem solved. I asked the homeowner if they wanted another one installed, and they said no. Lowes and Home Depot have them sitting on the shelf, so I'm guessing they sell enough of them to keep them stocked, but I just don't see them anywhere. I don't have one in my house.

I only have them on my floor heat circuits. My domestic heater circuit doesn't have one. But I don't store hot water either.

 

[grsthegreat]

I have one on my system. We have a whole house backflow preventer as required by state for our water district.

most every system i see has them, and ive never seen one rust out.

 

[TractorTYMe]

I have a Hubermeyer Foundry hotwater tank from Seattle dated 1949. When it blows it will probably level my house?

 

[ovrszd]

most every system i see has them, and ive never seen one rust out.

I wonder if there is some confusion about how an expansion tank works? Mine has a rubber bladder inside a metal tank. Not sure how it can rust out? But I only have 5 years of ownership to go by.