How to pressure test new water lines?

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James Stephens

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I'm a homeowner building my own small house along with contracting out parts of the work. I'm a worrier by nature, and being involved in building a house may not have been the best idea but I'm more than halfway there. I'd greatly appreciate some knowledgeable advice about a plumbing concern...

I had PEX water lines installed (top out) and the plumbers air pressure tested the lines with a shraider valve and pressure gauge assembly. They tested at 30 psi for 24 hours, per code, and all was well. The gauge was left on the system, work stopped for 3 1/2 months, and I couldn't help but notice that the pressure slowly dropped a bit over that time, and ended up at 26.5 psi. Temperature changes seemed to make for swings of a pound or so but the pressure has definitely dropped aside from that factor. I realize this is a very small loss of pressure but I'm thinking that 3 1/2 psi could mean a drippy leak and who wants even a little leak. I guess that the loss could have happened due the shraider valve and/or fittings of the test assembly but I can't know for sure. I'd like peace of mind on this before putting up sheet rock.

If I retest the system, would it be best to hook up a garden hose and test with water so any leak would be easily visible? Freezing is not too much of a concern because I will be insulating and rocking soon and we're not freezing here yet. I could also reinstall the plumbers test assembly and air test with my compressor and spray soapy water on the fittings to ensure no leaks.

What do you all suggest? Am I nuts for worrying about a 3 1/2 lb loss over such a long time or is any loss still a possible leak? Should I water or air test? Any problems in using a newish garden hose to water test? What kind of soap (and dilution) would I use for an air test?

Please help asap. Thanks much
 

JRC3

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I'm no plumber but I wouldn't worry about a 3.5 psi drop after 3.5 months. Heck, that might be attributed to the PEX itself just relaxing a bit.

Will air permeate PEX like it does a rubber tire?

Seems to me like a 3.5 month test with that loss is way better than any 24hr test. IDK.
 

Reach4

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Will air permeate pex like it does a rubber tire?
I would have to think so, considering that PEX used for heating pipes has an "oxygen barrier".

An air test on copper can be up to 50 PSI
No air testing for plastic pipes.
 
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James Stephens

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I also wondered about PEX being slightly air permeable. Hadn't considered the possible expansion issue though. I get uncomfortable with speculating about such things though. Not being a scientist or having experience with such factors, unknowns make me uneasy. Seems like a leak test where I can see a leak or not would be definitive. I'm probably in one of those low risk/significant consequence situation. Man, I hate these but I know life is full of them.

I do appreciate the input
 

Reach4

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I get uncomfortable with speculating about such things though.
I am sorry to hear that.

Air passes much more easily than water. If you want an easy bubble solution, children's bubble solution is cheap and readily available. They sell a commercial solution to test for gas leaks where the gas pressure is about 1/4 PSI. So that holds longer.

A diplomatic plumber would say there is nothing in your extremely low pressure drop rate to worry about.
 

James Stephens

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Thanks for your diplomacy and thanks for the specific soap advice. I didn't mean to be critical about speculations when I'm humbly asking for help. I do appreciate your thoughts. I just meant that I would love to have a sure way to know that my lines are leak free and it seems the air and soap test (or maybe a water test) would give me some extra peace of mind.
 

Reach4

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I am not a plumber. I sometimes dig into stuff well beyond practicality.
 
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