Rough plumbing pressure test - real slow leak

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toad_s

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Hello folks,

I have a question about doing a pressure test on copper supply plumbing. For background I am adding an addition on my house and am adding a new kitchen and laundry. I am doing the plumbing myself.

The plumbing is all roughed in and capped on the ends, and I and doing a pressure test with air. For one section, I am getting a slow leak. It drops from 50 psi to about 45 in an hour and down to 10 psi overnight.
I can't find the leak with soapy water.

My question, is there an acceptable level of pressure drop ? Or should it be able to hold 50 psi forever ?

Thanks
Toad
 

WorthFlorida

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How is this one section closed off from the others or is it the hot or cold side only? Check the end caps and any valves, suspect a leak from the stem or even the schrader valve used to enter air. Check and tighten down any packing nuts on any valves.
 

toad_s

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Thanks for the replies so far.

I tested at a couple of points, before continuing on. The first was the hot and cold runs from the addition into the existing basement. Then I added a branch line from those to where the hot water heater it. It's this hot water branch that is losing pressure.

The branch is not connected into the existing plumbing yet.
The scrhader valve and gage is ok, i think, because it holds on the cold side, but the hot side looses pressure.

I'll check the nuts on the ball valves which shut off certain sections.

Then I'll cut the hot side into 2 sections and see which will hold pressure.

One part that I tested overnight lost about 5 psi, but the house gets colder overnight too, so it might be temperature related contraction only.
 

Reach4

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I tested at a couple of points, before continuing on. The first was the hot and cold runs from the addition into the existing basement. Then I added a branch line from those to where the hot water heater it. It's this hot water branch that is losing pressure.
Are you pressurizing the water heater? I think you imply yes. How about checking the T+P output for bubbles? Stick a jar of water under and up the drain pipe.
 

WorthFlorida

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Just connect the hot side to your existing plumbing with a valve and use water pressure to test it. Then just shut the valve off when done with the test.
 

Sylvan

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Only lines I ever test with air is gas lines such as Oxygen and natural

The problem with an air test is pressure temperature relationship

Air when heated pressure increases as it gets cooler the pressure drops
 

Taylorjm

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Only lines I ever test with air is gas lines such as Oxygen and natural

The problem with an air test is pressure temperature relationship

Air when heated pressure increases as it gets cooler the pressure drops


I agree. I think you are making too much of a deal with finding a leaking fitting with water. Just hook it all up with a shut off valve and turn on the water and see where it's coming from. It's not like your dealing with gas and will end up filling a wall cavity with gas and cause the house to explode. It's just water.
 
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