Leak (?) in New PEX 'B' system

[nickjr4]

Just installed a DIY Pex B system in a small house I am building. Testing with compressed air at 50 PSI shows pressure drop of about 1 PSI every 24 hours. I am using a delta multi-choice shower valve with test cap only (no cartridge) as the bridge between the hot and cold loops. I have taken the expansion tank out of the loop and the water heater is not installed yet so only the following are being tested;
1. Pex pipe connections to pex fittings with i-crimp ring clamps,
2. Ball valves (and delta shower valve)
3. Threaded nipple ends [includes shower arm] screwed to drop ear fittings and closed with brass caps

Could it be something other than a leak?

I have tried soap water/bubble juice on the connections but can't identify any leaks. All threaded joints are done with thick yellow teflon tape plus Rectorseal #5 pipe sealant.

All connections are still exposed since I didn't want to do the wall finish until I was sure the water piping was good to go. At this point I'm thinking just contact the utility company to turn the water on, fill the system and see if it drips anywhere. Would there be a downside to proceeding this way?

Thanks.

 

[Breplum]

Water, and even boost pressure for a while to check for leaks after you bleed all the air out.

 

[Sponsor]

 

[Reach4]

There is a relaxation effect which will drop the pressure if you did not condition the pipe. However having the pressure drop for many continuous days does almost sound like a leak. Did you put your leak detection fluid around the connections at the gauge to look for a bubble?

Testing with compressed air at 50 PSI shows pressure drop of about 1 PSI every 24 hours.

See https://terrylove.com/forums/index....pressor-pressure-regulator.55451/#post-406456
In the post by Chuckd83, particularly see step 5 after you expand the thread.

There is also a temperature effect. has the temperature been dropping over those days?

 

[nickjr4]

There is a relaxation effect which will drop the pressure if you did not condition the pipe. However having the pressure drop for many continuous days does almost sound like a leak. Did you put your leak detection fluid around the connections at the gauge to look for a bubble?

There is also a temperature effect. has the temperature been dropping over those days?

Pressure drop occurred over 7 continuous days. Tried fluid around many joints including where the pressure gauge was attached. Heating system is up and running so temperature has been fairly constant. I say "fairly" because my mini-split heat pumps struggle a bit to keep up when the outdoor temperature drops into the teens.

Maybe air is leaking from the system but water will not? I have heard that this is common.

 

[JohnCT]

Maybe air is leaking from the system but water will not? I have heard that this is common.

I haven't seen it, but I've heard the same thing - makes sense though.

Make sure you aren't losing pressure through the gauge you're using.

John

 

[John Gayewski]

Whatever your system pressure is take that times 1.5. Then test for 15 min. 24 hour tests are useless. If your pressure is going to be 50 psi test at 75psi for 15 min. There are too many variables at play in a 24 hour period. If gauge drops at all in the 15 min you have a leak. If it doesn't you don't.

 

[nickjr4]

Whatever your system pressure is take that times 1.5. Then test for 15 min. 24 hour tests are useless. If your pressure is going to be 50 psi test at 75psi for 15 min. There are too many variables at play in a 24 hour period. If gauge drops at all in the 15 min you have a leak. If it doesn't you don't.

That was the first thing I did. No measurable pressure drop in 15 minutes.

 

[Eman85]

Just temperature change will change the pressure more than 1 psi.

 

[nickjr4]

Update - I replaced all the brass caps on the stub-outs with ball valves. Had the city turn on the water, opened the main shutoff valve, opened each valve in turn to bleed air out of the system and left it filled with water under pressure for 24 hours.

No leaks observed. All connections seem to be completely dry.

 

[Integrity Repipe]

A 1 PSI drop over 24 hours is minor, but it's worth investigating before closing up walls. While a slow air pressure loss often indicates a very small leak, it can also be due to temperature fluctuations affecting air density or even micro-seepage through seals that might not show up under water pressure. Since you've already checked for leaks with soap bubbles and confirmed tight seals, filling the system with water is a logical next step. Water is denser than air and will expose even the smallest leaks more easily. Just be sure to monitor pressure once the system is filled, checking around fittings and threaded connections for any seepage. If you still suspect an issue, looking into a pressure test with a digital gauge for more precise readings could help before you finalize the installation.

 

[nickjr4]

A 1 PSI drop over 24 hours is minor, but it's worth investigating before closing up walls. While a slow air pressure loss often indicates a very small leak, it can also be due to temperature fluctuations affecting air density or even micro-seepage through seals that might not show up under water pressure. Since you've already checked for leaks with soap bubbles and confirmed tight seals, filling the system with water is a logical next step. Water is denser than air and will expose even the smallest leaks more easily. Just be sure to monitor pressure once the system is filled, checking around fittings and threaded connections for any seepage. If you still suspect an issue, looking into a pressure test with a digital gauge for more precise readings could help before you finalize the installation.

System has been filled with water under pressure for 10 days now. No seepage observed. Everything still dry.