I have a strange problem with water blowing out of the water heater when the commodes are flushed.

Two story walkout with the water heater and furnace/AC in a downstairs closet next to the garage wall. Two baths upstairs. The two bathrooms are on a single vent; the kitchen on a different vent.

The AC condensation line and water heater TPR valve each share a plumbed line that leads to the main sewer line. The line from the water heater goes down to a cup-like fitting in case of leakage. It’s a catch cup open at the top.

Several week ago we began seeing water intermittently in the closet floor going into the garage but couldn’t find where it was coming from. Today we discovered that if we flush either commode upstairs, water streams from the TPR valve, fills the catch cup and line so fast that the cup overflows into the floor. The sinks and showers do not do this, just the commodes.

My first thought is to change the “Rube Goldberg” setup the air conditioning man put in for the AC and TPR valve to drain, and seal it tight instead of a catch cup, but the problem may be bigger than I thought.

Any suggestions are welcome. Thank you.

Earl

Earl, do you know what the water pressure, in PSI, is at the house? I'm wondering if it's very high and just below the set pressure of the TP valve. When the toilet fill valve shuts off, maybe a spike in pressure opens the TP?

I don't know the pressure, but it's never been high. If anything, it's a bit low. I know that my wife has often said "boy, we don't have a lot of pressure". Were in a small rural county--kinda' small, but I will check the pressure.

Thanks for your idea.

Steve, I had my son flush one of the commodes and hold the flush handle down so the fill valve stayed open. Still got water so I'm still wondering. Thanks, Earl

the 'catch cup' sounds like a funnel with air break for the TP and the AC condensate lines

the lines should end ABOVE the funnel (which would make an actual air gap), but many less than knowledgeable mechanics will insert the lines INTO the funnel


are you SURE the funnel ITSELF is not overflowing when you flush ?


that would indicate a partial stoppage in the main 'sewer' piping

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

I think you are misdiagnosing the problem. The "cup" is probably connected to the sewer system and when the toilet flushes SOMETHING, either air pressure or sewage backflow, is forcing water out of it, but NOT from the heater's T&P valve.

? did I not just say that ?

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Posts must have crossed.

I think I’ve found the problem.

We flushed out the drain lines with high pressure from a hose nozzle, and could hear the water running through the line in the garage to the sewer line. Then I moved the line from the TPR valve out of the cup. We flushed the commode and got NO water from the TPV valve (you both were right), but a blow back from the cup. We disconnected the drain line from the sewer line in the garage and flushed the commode. Water ran for a moment and then blew out of the sewer lines.

Conclusion: there is a blockage (not completely) in the sewer line between the garage and the septic tank.

On my day off tomorrow, I will rent an electric auger and clean out that line and see what happens.

But I have a related question. How reliable is the TPR valve? If it fails, the cup and drain line cannot handle the load of water. Can I do some plumbing, get rid of the cup, and connect the drain line directly to the line from the TPR valve? Is this a good idea?

Thanks, Earl

Might be a second posting.

I think I’ve found the problem.

We flushed out the drain lines with high pressure from a hose nozzle, and could hear the water running through the line in the garage to the sewer line. Then I moved the line from the TPR valve out of the cup. We flushed the commode and got NO water from the TPV valve (you both were right), but a blow back from the cup. We disconnected the drain line from the sewer line in the garage and flushed the commode. Water ran for a moment and then blew out of the sewer lines.

Conclusion: there is a blockage (not completely) in the sewer line between the garage and the septic tank.

On my day off tomorrow, I will rent an electric auger and clean out that line and see what happens.

But I have a related question. How reliable is the TPR valve? If it fails, the cup and drain line cannot handle the load of water. Can I do some plumbing, get rid of the cup, and connect the drain line directly to the line from the TPR valve? Is this a good idea?

Thanks, Earl



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NO!!!!! It either has to go above the "cup" or to the outside of the building. It cannot be connected DIRECTLY to the plumbing system.

Thanks, HJ, that's a pretty emphatic "no". I really appreciate that, and I will back off of my idea. Thanks so much.

I could have made it a bit more emphatic, but I thought that was enough.

NO

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Just a bold "NO"?

you already had it under control



==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Everything is working fine now. It was a partial blockage in the sewer line between the garage and septic tank. Two runs with the electric auger, a hose in the line for 10 minutes, no more backup

Appreciate the help from all of you.

Earl



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