Brandon Weiss
New Member
I’m doing an air pressure test on the rough-in I just finished for my house and am confused by something that is happening—I’m not sure if it’s normal or not.
The house is about 1,400 square feet with a kitchen, two bathrooms, and laundry hookups in the garage. The supply lines are Uponor PEX which terminate at a variety of Sioux Chief stop valves and well-made mixing valves for the bath, shower, and lavatory faucets (they’re in-wall).
I made a little pressure testing rig using a sharkbite fititng, a tee, a gauge, and the standard air connection (schrader valve?). I put that on one open pipe and then capped all the rest. I opened the mixing valves so that both the hot and cold lines would be tested at the same time. Then I brought it up to 100 PSI.
The system holds at 100 PSI for 15 minutes with no problem (and it passed inspection). After a full working day (about 8 hours) I noticed it might have dropped every so slightly. At most like 0.5 PSI. Although it’s possible I’m imagining it, because shifting your head even a little bit while looking at the gauge can make it read slightly differently.
But here’s where it gets a little weird. I come in the next morning expecting it might have dropped 1 PSI, but it’s actually dropped like 50 PSI. I work another 8 hours, check the gauge, and it’s in the exact same spot. I come back 16 hours later, and it’s dropped another 50 PSI and now reads 0 PSI.
I do the test again, and this time it drops by less each day, ultimately ending at around 10 PSI. And for the last few days it’s mostly held right there. Maybe it dropped another few PSI.
I’m pretty mystified by this. My best guest is it has to do with temperature? During the day it’s about 55°F and at night it’s about 40°F. So maybe the air is compressing and the pressure is dropping overnight. Although I would think it would expand during the day and the pressure would go back up. Maybe there’s also a slow leak, but then I don’t understand why it doesn’t leak at all during the day, and leaks a lot overnight, when theoretically the pressure should be lower because of contraction and thus leaking less
Thanks so much for any advice!
The house is about 1,400 square feet with a kitchen, two bathrooms, and laundry hookups in the garage. The supply lines are Uponor PEX which terminate at a variety of Sioux Chief stop valves and well-made mixing valves for the bath, shower, and lavatory faucets (they’re in-wall).
I made a little pressure testing rig using a sharkbite fititng, a tee, a gauge, and the standard air connection (schrader valve?). I put that on one open pipe and then capped all the rest. I opened the mixing valves so that both the hot and cold lines would be tested at the same time. Then I brought it up to 100 PSI.
The system holds at 100 PSI for 15 minutes with no problem (and it passed inspection). After a full working day (about 8 hours) I noticed it might have dropped every so slightly. At most like 0.5 PSI. Although it’s possible I’m imagining it, because shifting your head even a little bit while looking at the gauge can make it read slightly differently.
But here’s where it gets a little weird. I come in the next morning expecting it might have dropped 1 PSI, but it’s actually dropped like 50 PSI. I work another 8 hours, check the gauge, and it’s in the exact same spot. I come back 16 hours later, and it’s dropped another 50 PSI and now reads 0 PSI.
I do the test again, and this time it drops by less each day, ultimately ending at around 10 PSI. And for the last few days it’s mostly held right there. Maybe it dropped another few PSI.
I’m pretty mystified by this. My best guest is it has to do with temperature? During the day it’s about 55°F and at night it’s about 40°F. So maybe the air is compressing and the pressure is dropping overnight. Although I would think it would expand during the day and the pressure would go back up. Maybe there’s also a slow leak, but then I don’t understand why it doesn’t leak at all during the day, and leaks a lot overnight, when theoretically the pressure should be lower because of contraction and thus leaking less
Thanks so much for any advice!
