TPRV drain Config questions

So…here I see a TPRV drain discharging into other drain pipes (I know they cannot share). The TPRV drain pipe “T” is loosely connected forming a an air gap of sorts. Also, the drain pipe is “vented” such as the top cut-off.

I would prefer to see a drain receptor for the condensate and TPRV drain pipes with an air gap. My questions are, what is the consequence of this configuration? Is the floor drain large enough to accept all three…the TPRV drain pipe, AC condensate drain pipe and the drain pan pipe?

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In three words… ‘Oh Hell No’!!


I don’t know for sure if I understand your question completely, but what if a child were to put something in the open pipe top and it got lodged where my red line is?

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Is that PVC or CPVC for the blow off? :thinking:

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JJ’s got it right!

@tglaze PVC

@jjonas @ruecker

JJ, you’re right and it was quickly called out. I went back for a reinspect and it had not been corrected.

My client asked a reasonable question, we know it’s wrong, but what is the consequence? Which got me thinking and decided to put it on the forum for debate.

(I was in a hurry. I should have phrased my question better)

The only code violation I can see with the water heater (and could be wrong) is that the tpr is sharing a drain line. I would just recommend the tpr tube be cut to discharge into to drain pan, and the condensate has an air gap.
Only way it could possibly be a problem at that point is if the water heater drain pan was filling, but even that may not overload the drain

Edit- also no p- trap on the condensate

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In my opinion, the scalding water and/or steam has an almost equal chance of going up, or going down. Slightly in favor of down due to gravity but if there is any restriction in the down direction, than up it might go!


Right. Steam up in your face and water down. I’ve never seen one actually popping off because over temp pressure. Only small intermittent discharge or dripping.

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Remember the original intent for the Code… prevent personal injury for person(s) nearby at the time of TPRV discharge…

Also… is there a drain line for the pan to drain ???


Neither have I actually. Even during an actual over-heating event, I would have to think the discharge is intermittent and not under tremendous force except for right at the valve termination. I will have to look for a you tube video I guess.

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Here are some on a much larger scale, lol.

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All three drains intersect at the floor drain (1) which seems small to me.

Number (2) is loose, I can lift the TPRV drain pipe out which appears to be a half ass attempt at an air gap.

Good point about personal injury.

I’ll send that to my client and tell him to insist on correction.

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Surprisingly, a quick search didn’t turn up any actual water heater valves going off. Now I really want to see one. I’ve seen the exploding tanks but that’s when the valve is plugged or inoperable.


That’s because they don’t blow off like in that video. Those look like Kunkle steam valves.


OK. didn’t realize that went into the floor as a drain.

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The probability of all three having water at the same time is tiny. Multiple the percentages: .001% x .05% x .0001% is almost never. I my area we’d be far more concerned to brace the water heater against quakes ;-).

Hot water could flow back into the drain pan, as @jjonas said.

But is that really a floor drain? Or just a hole in the floor that leads to a crawl space? Are the pipes sloped, or might condensate water drip back to the pan and rust it?

A very easy improvement to this setup is to cut the TPR pipe at the elbow and extend it down to the pan. Now you have a setup where any discharge from the TPR is observable AND it will still drain to the outside. If you’re uncomfortable with that: hundreds of millions of water heaters were installed before outside drains were even a thing.


True, and millions of house didn’t have toilets. Just a hole in the ground with a wooden shed :smile: