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

[newbury]

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"?

 

[PlumCrazy814]

I do not have an expansion tank and probably never will. Mine is electric, not sure if that makes a difference in the code. I don't pay attention to things and did not research, but I haven't heard of one popping. I have a well so I suppose the bladder in my pressure tank might act as an expansion tank in the system but IDK. Only time I've had to replace is when the old heaters sprung leaks due to corrosion. I do have an iron filter and a softener but not sure that helped extend the life at all on my last heater.

 

[lman]

I don't have an expansion tank. My electric water heater has been working since 1995. I have a well with a water softener and a second unpowered water heater that acts as a preheater from my geothermal system and plumbed into my water heater. I did replace the relief valve once.
I don't see any reason my water heater won't make it to 30, so I guess it's working fine without an expansion tank.

 

[Alan W.]

Ive never had one in my home that I built in 98 but they are required now by code.
My system hasn’t had any leaks due to thermal expansion.
My fathers house built in 63 never had one but when I changed out his water heater last year the relief valve would drip overnight or during the day if they were gone for the day.
He thought the valve was bad and changed it with no improvement.
I installed an expansion tank for him and it hasn’t leaked since.

 

[oosik]

I installed an electric hot water heater when we built the house here in 1982. I had to replace it eight years ago. The original tank began leaking. I've never heard of the use of an expansion tank.

 

[dodge man]

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.

 

[ultrarunner]

Many homes and never had one… even one mid 50’s home with a copper Hoyt water heater with no PTRV as it predates.

I have had to add a few whole house water pressure regulators as static on some places 180+ psi

 

[LouNY]

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.

 

[orezok]

If your water meter doesn’t have a check valve then the entire water system is your expansion tank. When the water heats it expands back into the system. If there is a check valve, it has no where to go and trips the temp/pressure valve to leak.

 

[ovrszd]

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.

All good points.

My hydronic floor heat uses tankless heaters as well as our domestic water supply heater. System water pressure against it all the time. Check valve to protect the system from water that's in the floor system. Expansion tank to protect the floor heat system from cyclic pressure changes.