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Discussion Starter · #1 · (Edited)
Hi all -

My water heater has a T off from the hot line that runs though a pressure relief valve, and eventually exiting outside on my patio. I'm not sure why it's there but maybe the original builder (about 22 years ago) did that because there's no drain in case the heater's TPR valve triggers (I keep a bucket under the heater's TPR valve pipe but it's never opened).

Anyway, that ~22 year old, secondary pressure relief valve opened and won't close, and I've got a steady hot water loss through it of about a gallon per 10 minutes. This valve is adjustable but when I took pressure off the system and tried to adjust it, the valve itself started leaking (great, now I've got TWO leaks).

So I'm just planning to cut that T out and remove all the pipe to/through that secondary pressure relief valve, and replace the T with a straight-line connector on the main hot water pipe.

Here's the question: Normally if replacing the WH I'd shut everything down, open taps upstairs, drain the tank and the house. But what if I let the tank cool, shut off the water supply and blow off pressure (if any) using the tank's TPR, then cut into the hot pipe to remove that T fixture without first draining the WH tank and whole house? In a 2 story, 4 bathroom house with the water heater in the basement, how much water would come crashing down on me?

Is it crazy/stupid to even attempt this?

Many thanks in advance. The only reason I thought of this is the last time I got a lot of air in the system, we had pretty bad pipe squeal for months.
 

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I am trying to understand your situation better.

What you are calling a pressure relief valve sounds like it may be a check valve which allows water to go only one way. When they fail, water comes out the relief part and doesn't stop. That's what may need to be replaced.

The temperature pressure relief valve is on the wh. and blows off when the temp/pressure is very high.

Post a picture of what you are talking about. Thank you
 

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Discussion Starter · #3 · (Edited)
Hi Jmon; thanks. I understand about the T&P relief valve on the WH itself.

The secondary valve is an adjustable Watt's pressure relief valve (pressure only, not a T&P). Hopefully the image comes through. The hot water line runs straight up from the WH into the main floor for home hot water supply, whereas the T-off pipe having this PR valve runs horizontally off the hot water line, then runs vertically up to the joist level in the dead space above the basement's drop ceiling, then uses this PR valve as the 90° turn to again run horizontally along the dead space out to the exterior wall.

I'm not planning to replace it because it really doesn't need to be there.

My main question is I was just wondering if possibly - with no open taps in the main floors of the house - I could get away with cutting into the pipe without getting drenched. Sort of the way water will mostly stay in a vertical straw despite having been lifted from the water cup, as long as the top of the straw is blocked.

Probably a stupid question, but hey! :smile:
 

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If you want to do that you will need to shut off the main water and open the faucets to relief the pressure otherwise you will get drenched.

There will still be a little water left over that will come out so be prepared for that.

Do you have an expansion tank installed on the wh like this?

 

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mineral deposits may have formed inside of it and causing it to not function/close correctly anymore.. Post a picture of your set-up in the basement. Thank you.
 

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Discussion Starter · #7 ·
Yeah, expansion tank on the cold side. I installed it with this WH about 10 years ago but failed to trace the T-line coming off the hot side and didn't notice this 2° PR valve setup.

I did a lot of searching online before posting here and it seems this getup was occasionally seen ~ 25 years ago but never common, and rarely used today. The comments I read tended to indicate it was used if the area around the WH was finished but there was no handy place for the T&P relief valve to drain if it opened.


If my local big box stores weren't really tough to get into right now due to "shelter-in-place" [1] I'd probably just go ahead and replace this WH at the same time as I'm doing the other stuff, given it's 10 years old.

[1] They're limiting visitor counts and the line to get in has been 30-50 people deep when I go by there. Luckily I've got on hand what's needed to cut out that T and couple the pipe back up.
 

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How much water is in your hot water pipes?

We don't know, all depends on how big the pipes are and how long.


To cut out that valve;


Turn off the cold water stop valve to the water heater.
Open the hot side of all your faucets and shower.
Open the water heater drain valve and let out about 5 gallons of water.
Cut out the valve. You may get a pint of water. All depends on how close to the pressure relief valve you cut. If you want to avoid that cut pipe at the pressure relief valve (or drill a small hole in the piping close to it).
Don't forget to close the water heater drain valve before turning the water back on.
 
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