Do I have a leak? Pressure lost on PEX Test

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Mathelo

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I've been pressure testing my PEX rough in over the last few days and I can only assume that I have a leak but I wanted to confirm before considering next steps. I'm using one of these http://www.pascospecialty.com/catalog/PASCO_CATALOG_F.pdf
to check the pressure and I followed Uponor's procedure to prestress at 120 psi for 30 minutes and then brought down to 80 psi. For all intents and purposes it held at 80 psi for 2 to 3 hours. However, over 60 hours the pressure has slowly dropped to 55 psi.

Is there anything normal about this or do I simply have a slow leak somewhere?

Thanks!

Louis
 
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hj

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The tubing may be "expanding" slightly after it is under pressure for that long, which would drop the pressure a little. If that is the cause, it should stabilize, at some point, and not drop further.
 

Jadnashua

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Also keep in mind that the air temperature will affect the pressure in that closed system, just like it does in your car tires...but, only about a pound/10-degrees.

Are the ends capped, or are there valves at the ends? Your piping may be fine, but the valves are leaking.
 

Mathelo

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Also keep in mind that the air temperature will affect the pressure in that closed system, just like it does in your car tires...but, only about a pound/10-degrees.

Are the ends capped, or are there valves at the ends? Your piping may be fine, but the valves are leaking.

This is just a rough-in so there are no valves yet other than the air test gauge with a schrader value on it to fill and measure pressure. The ends are all capped with EP plug fittings and Uponor bands. There is only a single EP T fitting in the PEX. PEX is 3/4" with a 1/2" branch.

I understand that temperature will have an effect but it should do up too. This pressure has been going in one direction. I started the test on Sunday with the 120 psi prestress. Lowered it to 80 psi and looked fine that night. I decided to leave it on for a longer-term test and monday night I notice about a 10 psi drop. I repressurized it to 80 psi thinking it might have just been temperature change but it repeated the same pattern the next day and this morning it was down to 55 psi. I suspect the air test gauge but I really have no basis for that. I've read elsewhere that if it holds for 2 to 3 hours I should be good but this slow drop has me concerned.

I'll get another reading tonight.

Louis
 
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Reach4

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You could try making soap bubbles. Use the kind of solution you would use to look for a slow tire leak... a strong solution of dish washing soap can be good, but the kids bubble solution might be better. Check joints starting with the pressure gauge.

Raise the pressure to 120 PSI to make bubbles better.
 

Mathelo

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You could try making soap bubbles. Use the kind of solution you would use to look for a slow tire leak... a strong solution of dish washing soap can be good, but the kids bubble solution might be better. Check joints.

Raise the pressure to 120 PSI to make bubbles better.

Yes, I think that is my next test.
 

Jadnashua

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The Schrader valve seals with a simple rubber gasket...they make a simple tool to tighten the core up. Or, just get a good valve cap for it (one that has an internal gasket), and that should help. It should be easy to check with some soap if that's it.
 

Mathelo

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I've not yet had a chance to check this out more carefully. Will have to wait until the weekend but it is still losing pressure. So either I find a proper Schrader valve cap or I put a proper shutoff at the gauge.

First step will be some soap.

Louis
 

Mathelo

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Found the leak.
2014-03-08 10.55.04.jpg

Inserted a hose washer and double taped. Holding now.
2014-03-08 11.32.35.jpg
 

Terry

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attachment.php


That happens to be the most common cause of a test leak. The threads where you attach the gauge.

I hadn't commented before, because it's almost impossible to get leaks on a Uponor PEX system.
 
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Craigpump

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And if you do have a weep with Uponer, a little heat from a torch or heat gun will contract the ring enough to eliminate the leak.
 
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