Pressure dropped during construction


Bronze Supporter
Jul 16, 2019
Laguna Hills, CA
When the plumbing on our pool went in, the pressure was slightly under 40 PSI (maybe 39 PSI). It's been about 3 weeks, and I noticed the pressure is new around 36 PSI now. The pipes are slightly covered now (to allow the workers to move around more easily) and the temperate in our area has dropped within these last 3 weeks (maybe 5-10 degrees during the day and more at at night). Would that account for the difference in pressure or should I be worried about a potential small leak? I'd figure if I had a real leak the pressure would have dropped considerably more.


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pressure drops about 1psi for every 10 degrees.

Talk to your PB about the pressure drop but I would not be overly concerned Unless it continues to drop.


Silver Supporter
In The Industry
Aug 15, 2017
Spring Valley, NY
Three weeks and a pressure drop wouldn't worry me. If the pipes had a leak it would've come through in 2 days if not less. 3 psi is temperature related and or the fittings for the testing used.


Well-known member
Jun 10, 2019
Urbana, MD
40PSI seems like a lot, it is usually like 20psi but I could be wrong.. Is it air pressurized or water pressurized? water will hold pressure longer on the system


Well-known member
Jun 10, 2019
Urbana, MD
I’m assuming air, but I don’t know for sure. This is a pool under construction.
The system should be under pressure at all times until the plaster phase in order to ensure that there is no leak in the plumbing.. When my pool was built, the plumbers did tested the pressure with air at about 30 PSI.. A couple of days later it was lower, like 25 but i spoke to the PM and was told that this was normal. He then later before the deck phase when the holes are filled, he filled up the system with water to 20 PSI and that did held very well until plaster which occurred about 45 days later, it was maybe 18psi..