Pressure testing with air versus water

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AJay

Moron
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Have finally gotten back to work on the bathroom project and am about ready to finish gluing and screwing down sub0floor as well as starting to put up some of the backer-board for the shower.

Up to this point, I have only been testing the copper supply tubes with air from my compressor and am confident that there are no leaks.

However, I haven't actually put water into the system, part of which isn't complete as I don't know exactly how the piping for the tub will go. This is because I will likely have to modify the tub frame.

Two thirds of the sub-floor is already down so if there is a leak I'm in big trouble.

But there were no leaks with the air, which I confirmed with soapy water sprayed over all the soldered joints.

Part of me is telling me to test with water what I have installed (using Shark-bite ends caps on the unfinished stuff) while another part is telling me that if it holds air it will hold water.
 
Did you pressurize the system and maintain that exact pressure for 24 hours? If so, you are good to go.
 
I left it at 90 psi for about 6 hrs. But I guess I should fill it up again. Is 90 high enough?

I realized even if I put water into it, without any fixtures at the ends to let the air out it might not be a good test.
 
I;m sure John or others will chime in soon but as long as you seal the pipes, using a schrader valve and a gauge, and pressurize for 12-24 hours, without any drop in pressure, you will be good to go.
 
I have a gage attached to a shark-bite fitting, then a shark-bite valve to close off the air on another pipe. The air crosses from cold into hot piping in the shower value rough in thing.
 
The way we tested most of are lines was with air. We would cross connect the hot and cold the pump them up to 100 PSI. In most cases water wasn't available and even if it was we would still use air. We also use air to test gas lines, but not with that high of a pressure.

John
 
For once, I disagree with John. Air for gas lines, places where a leak dribbling water would be unacceptable, or in a copper system that I need to be done with ASAP, and water trickling into any repair area would make resoldering a leaking joint difficult. Otherwise, I much prefer to fill it with water, than take it up to test pressure. With waterpipe, the higher the better. My minimum is 200 PSI for a water system, and I actually prefer higher. Not much that will leak later will hold against 250 PSI.

Particularly on the larger systems that I typically deal with, it is very time consuming to walk around and spray every fitting with soapy water, and I have seen defective piping in the middle of a section that was an absolute bugger to find (black iron pipe in a natural gas system). Then there was the slightly damaged 2" DWV test cap that kept me on a house underground for an extra 2 hours digging all of the dirt from around the fittings and soaking everything trying to find it.

All of that said, with a copper piping system, you are most likely just fine. I have seen plastic piping systems hold with little or no suggestion of a leak at 100 PSI, only to fail down the road. But if you have pumped it up and sprayed every joint with a heavy soap and water solution, you should be good to go.
 
Phishfood, I was under the impression he was working on a small addition not a large building. And testing copper water lines. I don't think were comparing apples with apples.

John
 
Well, I appreciate ALL the replies to questions as I learn a lot.

Of course, I certainly don't have the means to perform a 250 psi hydro test.

I also visually check every single solder joint with a small mirror and flashlight to ensure I can see silver all the way around.

Thanks for all the replies.

AJ
 
When we were doing new work in the North East most of the homes were two story with 2-1/2 baths. All we were using was copper water lines. We would test with air at 100 psi. If the pressure remained the next day we would consider it tight. Keep in mind these homes all had basements and all the piping was visible. If it didn't hold we would simply walk around looking for the problem. There were some times when they were hard to find. At that point we would bump the pressure up to 200 psi. That made the leak very easy to find and repair.

John
 
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