Thermal Expansion Tank--Required?

1973 model home experienced the installation of a replaced gas water heater. Despite the pitiful copper soldering and the device listing 15 degrees from a perpendicular orientation (compromised subfloor), my attention was focused on the absence of a thermal expansion tank. I wrote it up stating the manufacturer recommends installation of an expansion tank and also directs the installer’s attention to local building codes.

The agent calls me today to inform me the seller consulted with the building department. They inform him that expansion tanks are required on new construction only. It has always been my understanding that new installations must follow the most recent building codes, not necessarily the enforcement of the building department. I’d like to hear others’ advice on this matter, please.

Thanks in advance,


It would be nice it the local AHJ’s had the power and discretion to make enforcement More strict (without the option to be less restrictive)…

Unfortunately not the case…

If they say it okay, you’ve done your job with the deferral.:roll:


Are you saying that the AHJ stated that exp. tanks are required for new construction, but not for new installations in older homes? That doesn’t sound right.

Absolutely. I am going to call the building department myself to confirm. I’ll post my experience.


Today I had a hydronic system with no visible expansion tank about (5-8 years old). The house was older, so I went up and double checked the attic space / closets / knee walls, thinking there might be an old one up above the radiators. I found none. I wrote it up.
As far as I know, all systems like this should have an expansion tank. I have one on my system and it is original to the home.


  1. Did the local AHJ come out and inspect it and render an official, written report. HIs do. Local AHJs will disavow and opinion goven over the phone.
  2. If the manufacturer of the replacement water heater requires an expansion tank (most do), the local AHJ doesn’t matter. Maufucturer’s installation instructions ALWAYS supercede mere local codes.

Hope this helps;

This is where you invited trouble.

You instructed someone in your report to go ask questions.

I see so many home inspectors get involved in conflicts because they are so quick to defer responsibility of final assessment to someone else to support their allegation of defect.

Opening things up to interpretation should be avoided whenever possible. The only time I defer further evaluation by another contractor is when you can not determine the operating condition of something because it requires repair before further evaluation can be made. Then I spell out specifically what I want the contractor to do because they probably won’t do it if I don’t write it out!

If there is a defect, report it and document all facts concerning the defect.
If it’s broke, “the component does not function as intended”. It needs to be repaired.

Document the ramifications of not performing minor repairs or maintenance.
Let the client decide if it’s important enough to follow up.

When citing building codes, you open yourself up to conflict due to multiple interpretations of the code.
If there is a code violation, just site the condition and the potential ramifications of its existence. This is the same reason that the code was adopted in the first place.

Don’t use words like will break, must be upgraded, is a violation etc.
Use words like may break, should be considered for upgrade, may be a violation.

[size=2]Under no circumstances should you report that someone screwed up by building it that way.
Simply report that construction of the component does not comply with expected building standards. Then described the ramifications for not constructing to the expected standard. When you say that installation does not comply with manufacturers guidelines, post a link or manufacturers directions in your report. Who can argue with that? It doesn’t matter that every builder in the state does it wrong, it matters that there is a specific ramification for allowing it.

Keep in mind that the enforcement powers of a home inspector comes solely from the clients check that is signed at the close of escrow!

It doesn’t matter what the manufacturer says, what the code interpretation is, or what other general contractors do. It’s all about the client.

I always tell my client that I do not fully understand their family dynamics (though I try) and I am not fully aware of what concerns me be important to them, so I’m going to report on everything I see. It is my opinion and my intention to bring their attention to these potential concerns so they are fully aware of what they are buying.

After completing my walk-through with the client (if they are present) or after delivering my inspection report, I always ask the client if they have any concerns about anything reported. If they have a concern, are they fully educated on the subject at hand? Do they need more information? If they say they have no concerns, I go over major issues I am concerned with to insure that they are fully aware of what they are diving into and are not receiving some bogus information from their real estate agent or their father-in-law.

We tend to get cranked up over stupid stuff we find, because we just can’t believe our eyes!
We need to leave our emotions completely out of our inspections as well as our opinions.

All the client needs is the facts. The facts about the defect. The facts about the consequences. The facts about what it takes to correct the situation.


Manufacture instructions are your trump all else is moot unless they conflict (lessen) code.

No need to defer, request/advise installation of the expansion tank and be done with it.

If the agent(s) or AHJ wants to advise client differently, that’s there dog in the fight not yours.

I’d place a call to my client expressing my concerns about others potentially providing misinformation.

from my reports
“In the event a qualified licensed contractor or expert disagrees with my statements, in this report, I suggest they provide written documentation supporting their opposition and sign their name to it.”


When consulting the AHJ to confirm, ask if the replacement of a gas-fired appliance (ie: WH or Furnace, etc.) requires a permit. If so, surely at that point, the AHJ would comment on the installation of an Exp. tank.

Makes you wonder sometimes, about who’s watching.