What is this fitting? → Pressure relief valve. → Weird pressure problems. → High water pressure!

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Flapper

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Can someone identify what this part is and what it is for?

xt8AD6e.jpg
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Flapper

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Thanks!! It came with a tankless water heater. I thought it was just a purge thing. I should put it back if it doesn't leak anymore. Or use another one if it does.
It has an arrow on it but I don't see why because water just goes straight through it so I don't think the arrow matters.
 

Flapper

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Our water heaters are Atmors and they suck. The terrible instruction manual said nothing about a pressure release valve (amongst other things), so I thought this was just a purge valve. On the first 13kw unit I installed, I included this fitting on the output, but after messing with it when doing connections or something, it started to leak through and wouldn't stop, so I just removed it. On the second 13kw heater I didn't bother installing it. Kinda scary that I actually left out pressure release valves. I'll put the working one on the first 13kw water heater; the second one has just failed, it's leaking from the canister. Only used for about 6 months. Atmor water heaters are crap.
The 6kw heater didn't come with a relief valve so apparently it doesn't need it.
 

Flapper

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Does the relief valve need to be on the outlet or inlet?
It seems that it does not matter. According to that manual, the arrow points towards the heater, not represent the direction of flow.
 

Smooky

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In the first link I provided it says: The safety valve should be connected to the cold water inlet pipe.
 

hj

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It is a pressure relief valve, NOT a T&P valve so it can be anywhere in the system. The instructions were written by someone who uses English as second language.
 

Flapper

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It is a pressure relief valve, NOT a T&P valve so it can be anywhere in the system. The instructions were written by someone who uses English as second language.
Hmm so can I use only one of these valves to protect the entire plumbing system?
Atmor is a dubious company that makes dubious water heaters and I would not buy Atmor water heaters again.
 

Jadnashua

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If your water pressure gets high enough to open that valve, it's doing its job. But, if that is the case, you really need a pressure reduction valve for your system as 80psi is the max you should have in a typical system. That would also require an expansion tank as the PRV creates a closed system. You might be able to get by without one with a tankless system, though, but still should have a PRV.
 

Flapper

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If your water pressure gets high enough to open that valve, it's doing its job. But, if that is the case, you really need a pressure reduction valve for your system as 80psi is the max you should have in a typical system. That would also require an expansion tank as the PRV creates a closed system. You might be able to get by without one with a tankless system, though, but still should have a PRV.
I'm pretty sure the valve was leaking, not that the pressure was high. We have a PRV.
 

WJcandee

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I'm pretty sure the valve was leaking, not that the pressure was high. We have a PRV.

That's what everybody says before the T&P valve gives way.

Or worse: "The safety valve was leaking so I removed it." "The safety valve was leaking so I wired it shut/plugged it/filled it with putty, etc."

These are the people who get the water heater through the roof:

Allstate Commercial

Mythbusters through roof

Mythbusters: Shock wave enough to be fatal

The neurotic New Yorker in me says that if you have a leaking emergency anything, one should actually test and ensure that it isn't leaking for a reason. Simple screw-on pressure gauge with telltales to give you the pressure over 24 hours. Expansion tanks are necessary in most places these days because the EPA is basically making local water systems require homes to be closed systems. Expansion tanks can become waterlogged, etc.
 

Craigpump

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I can't tell you how many times we see plugged galvanized nipples under a pressure switch installed on a tank with no Pressure Relief Valve, or the leaking PRV has had a plug screwed into it. Occasionally we see the tank in the yard after its gone through the floor, ceiling and roof...
 

Flapper

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That's what everybody says before the T&P valve gives way.

Or worse: "The safety valve was leaking so I removed it." "The safety valve was leaking so I wired it shut/plugged it/filled it with putty, etc."

These are the people who get the water heater through the roof:
It was a constant flow and opening and closing the valve reduced it but didn't stop it; I'm sure the water pressure was not high enough. If I knew it was a pressure relief valve then I would've fixed it or replaced it or something, but I thought it was just a purge valve thanks to the terrible instructions. I'll install the other new valve that wasn't used.
You said the haier says it should be on the cold water inlet side; would this apply to the atmor also? The cold water side has the filter on it...
 

Jadnashua

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If it were a T&P valve, it would need to be on the outlet as it senses both temperature and pressure. Since it's just a pressure valve, it really doesn't matter, but you do need to adhere to the water flow arrow on the thing when installing.
 

Flapper

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If it were a T&P valve, it would need to be on the outlet as it senses both temperature and pressure. Since it's just a pressure valve, it really doesn't matter, but you do need to adhere to the water flow arrow on the thing when installing.
If that is so then I need to put it on the cold side. But I don't see why theres an arrow because the water goes straight through it; it doesn't have a check valve in it.
 

Flapper

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I just discovered something very weird. I put in the other relief valve which was unused so it should be good. I connected it to the filter on the cold side. I think it was supposed to be connected to the cold side like that because the filter allows the valve to easily be connected, whereas on the hot side the valve would gorge the wall. So I installed it all hunky-dory and turned on the water...

It leaked through like the other one. But then someone flushed the toilet and it stopped. Then after the flush, it started dripping faster and faster.

So apparently when all outlets are off, the pressure builds up high enough to cause the valve to leak, and when an outlet is opened, the pressure is dropped and it doesn't leak, until all is shut off, then the pressure builds up and causes it to leak.

Reach4 said the pressure rating is 116 PSI. So apparently our water pressure is getting that high! Or perhaps it is getting almost there, causing it to make a small flow but not a disgorge. If the relief valve gets to its rating, is it supposed to start opening, or is it supposed to be completely open? Would it start opening before it reaches its rating?

We have a pressure regulating valve so it shouldn't be so high. But I think it is set to its maximum. The range is 25-75 so 75 is the maximum. The pressure shouldn't be so high. But maybe the pressure only increases a little bit (like 10-2o) and gets near enough to the relief valve's rating causing it to leak.

I'll get a pressure gauge and test the pressure. I suppose the PRV will need to be adjusted down.
 

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Jadnashua

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A PRV doesn't last forever. Until you actually measure the pressure, you won't know for sure, but it sounds like yours is toast.
 

Reach4

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We have a pressure regulating valve so it shouldn't be so high. But I think it is set to its maximum. The range is 25-75 so 75 is the maximum. The pressure shouldn't be so high. But maybe the pressure only increases a little bit (like 10-2o) and gets near enough to the relief valve's rating causing it to leak.
Maybe your expansion tank is bad. When you knock on the side while you are dribbling water from a faucet somewhere, the tank should sound empty.
 
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