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Old 03-17-2010, 09:15 AM   #1
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Testing new plumbing with air pressure


Has anyone used air pressure to test for leaks in new plumbing?
I plumbed a new double faucet shower, and don't have the final connections to the water supplies. But I wanted to test for leaks before I tiled without hooking up the water supply. So I soldered some threaded heads on the hot and cold pipes from underneath, put a threaded tire valve on the cold pipe and a air pressure guage on the hot pipe, and used the Delta dummy caps on the manifolds so air would flow.

I pressurized it at 90 lbs, and immediately found some leaks on the threaded pipes with soapy water sprayed on the fittings, and I fixed those. None of my soldered fittings leak.

My problem is I have now soaped and soaped and soaped and can't find any more leaks. But, I will lose pressure over 12 hrs and drop from 90 lbs to 60 lbs, then after 24 hrs it's down to 30 lbs. If it was a bike tire, it would be flat after 2 days.

My question is stupid, but...........I can't find a leak anywhere, and it's bleeding down. Do I still have a leak somewhere, or is this test over kill for what water pressure would be?
If I lose pressure over time like this, does that mean I will have a water leak too? Or is my test over kill for actual water pressure?

Signed, Baffled by No Bubbles

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Old 03-17-2010, 12:37 PM   #2
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Testing new plumbing with air pressure


No unfortunately your test is not over kill. In fact here in the chicago area some counties and/or villages require a mandatory 100 P.S.I. for 24 hours test of the potable water supply for all new or altered installations. This does not mean just what you are working on. It means the whole system in your home. Something is leaking and it must be found and fixed. 30 P.S.I. over 24 hours is a pretty good leak. We've had as little as a 4# leak in 24 hours and the inspector won't sign off on it.
Look at your gauge threads and the shrader valve also. In fact put a heavy soap solution (almost a paste) on all the threaded connections and pump it up to 100 P.S.I. and slowly and quietly check everything. A lot of times you will actually hear a 1mm bubble pop before you ever see it. Good Luck.

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Old 03-17-2010, 02:25 PM   #3
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Testing new plumbing with air pressure


Ok, thanks for your response. I'd be happy to fix it, I just can't find it!
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Old 03-17-2010, 05:09 PM   #4
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Testing new plumbing with air pressure


why not test with water? put a boiler drain (hose bibb) on one of your lines and fill.
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Old 03-17-2010, 05:44 PM   #5
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Testing new plumbing with air pressure


You really should check it with water pressure its safer and more predicable.
Fill it up and make sure all valves are shut off when you start the test.
People have used air and it got away from them and blew up water don't blow up it just leaks all over.
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Old 03-17-2010, 05:55 PM   #6
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Testing new plumbing with air pressure


are your fixtures connected? or just rough in
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Old 03-17-2010, 06:57 PM   #7
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Testing new plumbing with air pressure


Quote:
Originally Posted by tpolk View Post
are your fixtures connected? or just rough in
They're just roughed in. I'm using the Delta dummy plates, which are a pretty sweet deal that I haven't seen before.
I put the pressure up to 100 lbs, and soaped again and found one tiny (!) little leak at the threads to the manifold. Went thru the fix it drill again, and put 100 lbs back on it.
We'll see what the pressure is in the morning. I know it easier finding leaks with actual water, and I would have done it that way, but it's easier doing all the rest of the plumbing later on.

Thanks for the input, guys.
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Old 03-17-2010, 07:03 PM   #8
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Testing new plumbing with air pressure


wondered if you might be losing air thru the fixture
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Old 03-17-2010, 07:05 PM   #9
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Testing new plumbing with air pressure


Well, that was my first thought too. So I soaped the living daylights out of it, and no bubbles there.
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Old 03-17-2010, 07:09 PM   #10
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Testing new plumbing with air pressure


What PSI is required for the pressure test? The working pressure for water pipe and fittings is 175 PSI. Water is the best chemical to use, cheapest and safest. Do not use air on plastic! PVC and CPVC will shatter when it breaks.
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Old 03-17-2010, 07:17 PM   #11
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Testing new plumbing with air pressure


standard plumbing piping and fittings are rated for 125#.
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Old 03-17-2010, 09:11 PM   #12
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Testing new plumbing with air pressure


Usually our 'leaks' end up being the little needle in the valve stem we used to charge the lines.

Occasionally when testing with air, the leak will occur in a shower valve (air pushing past o-rings) and coming out of the shower head nipple. Capping showerhead will solve that issue.
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Old 03-17-2010, 10:00 PM   #13
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Testing new plumbing with air pressure


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Usually our 'leaks' end up being the little needle in the valve stem we used to charge the lines.

Occasionally when testing with air, the leak will occur in a shower valve (air pushing past o-rings) and coming out of the shower head nipple. Capping showerhead will solve that issue.
Thanks. That seems to be what's going on here. I don't have these kind of "leaks" when I hook up live plumbing.......maybe one or two.
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Old 06-17-2011, 09:03 PM   #14
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Testing new plumbing with air pressure


Hey niffumdutz, could you be more specific on that threaded tire valve connection to your plumbing, I have a raised slab to pour with pex tubing and need to check for leaks before the pour, I was thinking that maybe if I could find a way to connect a tire valve to the pex tubing, I could pressurize the tubes and check for leaks. but I don't know where or what exactly to ask for to convert and adapt to 3/4" pex.
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Old 06-17-2011, 09:36 PM   #15
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Testing new plumbing with air pressure


Livingdead : Are you puting down 3/4" pex in the slab for potable water or are you installing radiant heat?

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