1 psi pressure drop in 24 hours

[DTAZ]

I have a 1 psi per day pressure loss (a bit less really) on an 90 psi pressure test for bathroom plumbing. I have soaped every joint and fitting, including the shower mixing valve, and do not detect the leak location. I have a sense that one of the temporary nipples, which are threaded into drop ear elbows, are leaking. The system is a mix of copper (in the walls) and PEX (in the crawl space). For practical purposes, is that even a leak that would result in accumulated moisture and would it be better to simply charge the system with water and see if I get a drip? Thanks in advance.

 

[Reach4]

The pressure drop could be from the pex relaxing. You could drop your air pressure to 66% of what it is now, and see what happens to the pressure after 24 hours.
https://www.uponorpro.com/~/media/Extranet/Files/manuals/PLU_PressureTest_IS_0812.aspx?sc_lang=en

Also, the temperature can affect pressure.

I am not a plumber.

 

[Sponsor]

 

[LLigetfa]

I have a 1 psi per day pressure loss

How many days did you test? How consistent was the temperature over that time?

 

[DTAZ]

How many days did you test? How consistent was the temperature over that time?

It's been under test for a week and it's lost about 8 psi. A drop from 90 to 82. Temperature dropped with the onset of the monsoon rains. From the 100s down to the 70s over the last week.

 

[LLigetfa]

If the temperature dropped consistently over that time then it may be the loss of pressure was due to contraction. When I tested my plumbing in my new home, it was Winter and before I had the furnace installed so I could not keep the temperature consistent which affected the test results. I was fearful that I'd miss a small leak and soap testing found one leak. There was a small drop in pressure on the retest and further soap testing failed to find any more leaks so I chalked it up as temperature variation, closed up the walls, and hoped for the best. Since the furnace was not to be installed until much later, I would not test with water and was too frugal to test with plumbing anti-freeze. I pitched all of the piping to drain but did not want to risk it.

Much later, I found a very slow leak on a union on my shower and had to cut open the drywall on the backside to fix it. It was in a utility closet where the water heater was so I just left it open with an access panel.

 

[Reach4]

It's been under test for a week and it's lost about 8 psi. A drop from 90 to 82. Temperature dropped with the onset of the monsoon rains. From the 100s down to the 70s over the last week.

A temperature drop alone from 100F to 70F would explain a drop of 90 psi to about 84.4 psi, if I did that right.

 

[Terry]

1 PSI is nothing to worry about.