Define "Indirect Waste Receptor"

IRC P2803.6.1 states that the discharge pipe for a TPR valve “shall be piped full size separately to the floor, to the outside…, or to an indirect waste receptor located inside the building.”

** What is an indirect waste receptor?** I’ve seen that term used elsewhere in the IRC. Please see the attached photo of a TPR valve drain connected in the crawl space to the water heater pan drain line, which discharges outside the house. It this acceptable? Is that an “indirect waste receptor”? Is the crawl space “inside the building”?


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Yes, It is acceptable (it’s outside) and no that is not an Indirect Waste Receptor.

An indirect liquid waste receptor is a plumbing fixture designed specifically to collect and dispose of liquid waste from other plumbing fixtures, plumbing equipment or appliances which are required to discharge to the drainage system through a physical air gap or listed air gap unit.

The following are types of fixtures that commonly fall into the classification of acceptable indirect liquid waste receptors: **Floor sinks, mop receptors, service sinks, laundry tubs **and washing machine standpipe drains. Water closets of toilets in bathrooms are not acceptable as suitable indirect liquid waste receptors.

Thanks David. However, what is the meaning of the word “separately” in this phrase: "“shall be piped full size separately to the floor, to the outside…, or to an indirect waste receptor located inside the building.”

Does that not imply that the piping can’t join another drain?


A drain is a drain is a drain is a drain. Separately is implying that this TPR pipe needs to be on its own. But in this particular situation, these lines are not being used full time and are fine being connected together as they are. They are there for the sole purpose of ridding unwanted water to a convenient area if the water heater ever did fail.

The installation you have here is absolutely fine.

I would respectfully disagree with you on allowing the TPR valve to connect to another drain line. The TPR valve drain line should not be leaking/draining water unless there is a problem with the water heater or TPR valve. The reason for not mixing the TPR drain line with another drain line is to be able to identify water coming from the TPR drain line to alert the occupant of a potentially serious defect. If the lines are mixed, one may not be able to determine the source of the water draining in the drain lines. Consequently, TPR drain lines should not be mixed or connected with other drain lines and should terminate in a visible and accessible location.

Steve Taylor
Taylor Inspection Services, Inc.
Amelia Island Florida 32034

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This TPR valve drain line (in question) is connected to the WH pan drain line. Neither one of these lines should be leaking at any time and if they were, it would be pretty obvious to an average homeowner, hopefully.

It is always great to have the discharge end of these two lines visible at all times, so that the average person can monitor these lines on a daily basis.

So… all in all, having these two lines connected to each other is (in my mind) absolutely fine.

Now if this TPR valve discharge pipe was connected to a full time waste line (like you think it is) then it would be an advisable issue. But (like I said), neither one of these lines should be leaking, period.

If this discharge point was not viewable, and terminating in an area where it cannot be monitored (such as a crawl space), I would definitely advise my clients of the consequences.

I have two units with water heaters below grade. There is no sump pit and the main drain line is at about 40" off the floor.

There is enough elevation to pitch the T&P drain to the top of the washing machine standpipe, but that seems contradictory on three separate points.

  1. The standpipe is PVC. Is that allowable since there’s an air gap and it’s no longer part of the drain?
  2. The top of the standpipe is 60" off the floor, much more than the 24" allowed by code. I’m guessing that this provision would only apply IF the standpipe was 24" or lower?
  3. Regardless of whether points 1 & 2 can be overcome, the end of the T&P drain needs to be visible. I can’t see placing it above the standpipe next to the washing machine drain pipe.

Or am I missing something?

At this point the only viable option I have come up with is to install a sump pit and pump.

BTW, I am in Vermont, so terminating the T&P drain outside is not an option, even though there is sufficient grade for that (it’s a raised ranch so the basement floor is only about 30" below grade).

Comments? Suggestions?


I don’t think anyone has come up with the correct answer.
6 in to floor or indirect waist receptor. Visible air gap but not dangerous.
If to outdoors still need visible air gap.
Sounds like, need to bring air gap to bottom end of TPR valve discharge pipe. After that it’s just drain pipe; trapped, connections to other pipes do not matter.

Trapped , how do you keep trap wet?

Do you realize this is a 14 year old thread?

Anyways, to answer your question, under normal conditions, it could take 3-5 months for a trap to dry out.

Well, I bet it is dried out now! :rofl: