Simple question about home inspecting

How many of you test the air pressure in a expansion tank for the water heater?

There isn’t a whole lot of air in a hot water heater expansion tank. Testing the air may release enough air to render the expansion tank useless. Some expansion tanks have a red button that indicates they need to be replaced. To me it’s like testing a temperature pressure relief valve just stay away from that.


Bring an air pump if you are going to test it :slight_smile: The best thing to do is to make sure the pressure is within range on the pressure gauge of a boiler and the relief isn’t actively leaking, this pretty much tells you the expansion tank is doing its job. Keep in mind, the pressure gauges do break and may not be accurate. For WH, put a working gauge (if possible) on the water line, fire up the water heater and make sure it’s not going higher than static+10 psi of pressure.

I tap on it top and bottom. There is a big difference in sound of water filled and air filled top portion. If both ends sound the same, I figure it must be waterlogged. Just don’t tap too hard when they arent supported or their connection is rusting :wink:

Wouldn’t you first have to know if it’s summer or winter air? :thinking:

We have a lot of well systems where I am, and I always test the pressure in the expansion tank on the system.It should be 2psi below the pump cut-on pressure. I also test the expansion tank on a hot water heating system.
I don’t test the expansion tank on a water heater.

That is interesting I never gave that a thought, I have a battery operated drill looking air pump I thought I could use if I checked the PSI on a expansion tank and lost some air

Expansion tanks come pre charged. Why would you want an expansion tank to exceed home pressure by 10 psi, just curious?

I don’t want it to exceed, read what I wrote slowly.

PS: I am still waiting for you to give me sources for the sharkbite comments you posted.

I smell a Google Plumber.

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Some have very very slow learning curve :slight_smile:

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Do you do a water flow test in the bathrooms?

Is testing the air pressure in the expansion tank in our SOP?

You are correct Larry, it is not in our SOP. I do it on well systems since a lot of my clients are unfamiliar with well systems. I do it to verify the tank is not water logged/leaking. I do not want them to have any issues a few months after they take possession. That’s way I’m not cheap! :upside_down_face:

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No I do not do a flow test except for a visual, unless I overlooked it I did not see the testing of an expansion tank in the sop, but I have had some of my clients I do repairs for call me to replace a leaky water heater and when I get there the leak they are referring to is the tprvalve, which always seems to boil down to having there water temp set to high or a bad exp. tank. And I just thought about testing them for my home inspections to keep a dripping tprvalve from scaring them.

Joe, I can tell if the tank is water logged, or has a leaking line, by how fast the pump comes on when I am doing a flow test. It is easy. Try it sometime. Time yours and then time others. The faster the pump comes on and cycles the more water logged it is, I have found. YMMV. :smile:


I will do that Larry! Thanks!

As part of a general home inspection, never. But we all get to include whatever services with think appropriate. Bear in mind that each time you comment on something that exceeds the SOPs you expose yourself to increased liability, but If you are confident in your skills you may also be offering value above that offered by your competition. It really depends on how much time any such service takes and much liability it caries against how much additional value it adds.


Very good advice, really makes me stop and think on it

Excellent advice Kenton. If the home you are inspecting has a closed portable water system the best way to verify the expansion tank condition is to glance down at the drip leg off the temperature pressure relief valve. If you see water You’re likely to have a bad expansion tank or possibly a bad TPR valve. My money is on the tank.

I doubt the TPR valve is going off because the water heater is set to high that just doesn’t happen. I guess the question that comes up is if you are replacing or repairing plumbing for clients are you a licensed plumbing contractor?