We are having a new system installed. The ground loops have been laid and were air pressurized to 55 on Friday. The contractor gave us the go ahead to backfill over the weekend. On Saturday, I checked the pressure, it was at 38. Could not reach the contractor. I decided not to backfill until I could talk to him. Now, on Sunday, pressure is down to 30. I lost a day yesterday, and likely another day today. My question to the forum is this: Is this air pressure loss normal, or do we likely have a leak? Should I continue backfilling or lose yet another weekend? Thanks for the input! (and no, still no return call from the contractor).
Get out the soapy bubbles and find the leak. Check every and all fusion joints. Also check the schraeder valves themselves. Then you may be able to backfill everything but that joint.
HDPE Pipe will not hold a constant pressure because the pipe stretches. Air is a lousy way to test. If the loop is full of water, you can see the leak. You best bet now is to follow Chris's advice, add some more pressure and see if you have a leak. You might not have a leak, but with an air test, there is no way to know. Sometimes you can hear the air leak, but not always.
See IGSHPA Standard 1E.5 here- http://www.igshpa.okstate.edu/pdf_files/publications/igshpa2011standardssec.pdf
So that's where that 100psi comes from... I lean towards the gas industry's and pipe manufacturer's HDPE pressure testing methods as they better deal with stretch. Chapter 2 of the PE pipe handbook. Or just google.
IGSHPA is not doing anybody any favors with that publication. Doesn't even address pipe stretch. I am glad not to be paying them money any longer!!
When you pressurize a gas it gets warm. Then it gets cooled down to ambient temperature, thus a loss of pressure. That is normal. Behavior is very different with fluid filled pipes. The loss of pressure comes mostly from the fact that they are filled with air, which expands and contracts much more than fluid with fluctuating temperatures. The pressures usually stabilize after a few days. The opposite is the case with fluid filled pipes, where the HDPE expands and contracts more than the fluid inside the pipes. Going from 55 to 38 to 30 with air filled pipes I have seen before, without any leaks. See if the pressure stabilizes, and lets us know.
I use 100 psi as a benchmark, allow for cooling and then re charge to 100psi. If I see 90 the next day, no biggie. If in doubt flush the loops and test with a hydrostatic pump. Game over. Any plumber who does commercial work or fire systems can do this for you. Hope this helps Eric
We routinely pump loops full of water to 100 psi and they are 50 -6o psi over night. We pump to 100 again and it will drop to 70-80. For Commercial Jobs, we perform this test: The pipe is filled with fluid, purged, and the pressure raised to 120 psi (adjusting for ambient temperature over 73 degrees F). b. Over a 30 minute period add fluid to maintain (steady) 120 psi (adjusted and corrected for temperature). Record pressure in 10 minute intervals. c. After 30 minutes, rapidly (2-5 seconds) reduce test pressure to approximately 30 psi to 40 psi by opening and closing the discharge valve once. d. Record pressure readings for 90 minutes for the following time intervals: i. 5 readings at 1 minute intervals, time period 0 – 4 minutes. ii. 3 readings at 2 minute intervals, time period 5 – 10 minutes. iii. 5 readings at 4 minute intervals, time period 11 – 30 minutes. iv. 6 readings at 10 minute intervals, time period 31 – 90 minutes. e. A passing test is indicated by an increase in pressure without any subsequent loss of pressure.
