TRP Drain Line Question

Is the drain line from the TRP valve on a attic installed hot water heater allowed to drain in to the pan if the pan is plumbed:?:

yes, Peter

In LA it’s allowed (per the IRC), but not in states where the UPC is enforced, such as CA.



2003 IRC:

The standard pan used under a hot water heater is not acceptable to prevent the possibility of damage to the structure from a large flow of water, under pressure, when a TPR releases. If the pan were appropriately sized to prevent splashing and potential damage then it may be allowed.

I understand your logic Manny, but I’m not sure I agree with your interpretation.

The UPC is much more specific. . .

510.8 Relief Valve Discharge. Discharge from a relief valve into a water heater pan shall be prohibited.


Wish I had a copy of the UPC. Any links to an online version?

Basically what I am referring to is the size of most pans placed under water heaters are very meager. Most are barely big enough to hold a gallon or two of liquid and the edges are barely an inch high. If a TPR pops there is going to be a lot more water flowing than the pan can handle. Also it will wind up splashing everywhere when under pressure.

Probably a better explanation comes from the IRC Commentaries:



As I said, I understand and agree with your logic, however, your interpretation is not in line with common understanding as I know it. I believe that most code authorities agree that it is acceptable to discharge into the drain pan when referencing the IRC.

It’s allowed down here in San Diego.

I assume you mean that some of the AHJ’s turn a blind eye to it Russ. San Diego County follows the same California Plumbing Code as Los Angeles County.

Russel, does not list San Diego but the San Diego County WEB site does provide a reference to their codes then to . It appears San Diego county follows the California Plumbing Code which does prohibit this (see Jeff’s reference above ).

Not some. All.

Remember that the AHJ, and his/her interpretation, has the final say-so.

There’s really no other way that this can be interpreted.

I’m sure there are many AHJ’s in San Diego County that abide by the CPC. After all, most of them have never known any Building Code other than the UBC/CBC.


If that were the case, we wouldn’t be having this discussion. Witness:

The IRC is not as clear as the UPC/CPC.

It is quite clear by California Standards.

No doubt. Unfortunatley, it’s not quite as clear to some of those who carry out California Standards. I’m not a code enforcement officer, so I’m going to leave that to those who are.

Still debating this? The IRC does not allow it, the IPC nor CPC nor UPC allows it. If you would like to ask some experts there is a nice debate going on here about it:;f=2;t=001564

I’ve learned not to argue with the AHJ because that’s the final authority that my Clients and the Realtors go to. That’s usually how I find out about these things, usually proceeding like this:

Home inspector says ABC about plumbing and recommends further evaluation by a licensed plumber.
Client or Realtor calls for further evaluation by a licensed plumber.
Plumber says the home inspector is nuts.
Client or Realtor calls the home inspector to tell him that the licensed plumber said the home inspector is nuts.
Home inspector says to have licensed plumber put it in writing on his company letterhead, date it, and sign it.
If licensed plumber does that, then we’ll call the local AHJ and get their interpretation.
About 50% of the time the licensed plumber is correct. That, of course, also means that about 50% of the time the home inspector is not nuts. Considering that the licensed plumber, by virtue of his licensing, is supposed to be more knowledgeable than a lowly, unlicensed home inspector yet is wrong 50% of the time, this home inspector is pretty happy that he can hold his own with those licensed plumbing experts.

Now copy the above and, wherever “plumber” and “plumbing” appear, enter any other profession, such as “electrician,” “engineer,” “pest control,” etc.

Yep, this home inspector is pretty happy, as are his bankers, accountant, and employees.

Notwithstanding your mental status Russ :wink: , it’s wrong - the TPR cannot discharge into the water heater pan (in CA) - and I hope you would call it out as such.

There have been many instances where I have been asked to reinspect or amend my report to reflect the opinion of an “expert” who contradicted my findings. It ain’t happenin’ (unless, of course, I was wrong :smiley: ).

I would much rather have the contradiction of the inspection report and the plumbers written statement when it’s in front of a judge due to property damage or personal injury from (what I found to be) an improper installation.

Oh, yeah.
Question my mental status on Cinco de Mayo.
I understand.
That’s okay.
I never schedule inspections on National Margarita Day, so I’ll just have to get Dr Cuervo and his assistant, Ms Margarita to help me with my mental status.

You can ask me how I address it if you would like. I don’t “call it out as such,” but I do have wording methods for addressing things that I disagree with the local AHJ’s about, such as the TPR drain pipe terminating outside with a billion 90° elbows in the course of its one-mile run.

Fortunately (I guess), that has never happened to me. I have had several Top 10 Realtors advise me on how to write my report. Since they are Top 10 Realtors and have sooooooooooo much money, I have invited a couple of them to purchase my company so that they can advise themselves on how to write their reports. No one has taken me up on it yet.

So would I. That’s kind of like a duh! I think.
But the ol’ AHJ can still override the inspection report and the plumber’s written statement.