DWV piping won't pass pressure test

[tconner]

We have a new house that is 90% complete. The builder has been testing the DWV each time a toilet or p-trap was installed. Last week all was good.

This week we can't hold pressure against the p-traps. To troubleshoot, we pressed the piping up to 5 psi and looked for the leak. We couldn't find it. over about an hour we lost 1/2 psi.

we split the house in half and found that south side has the leak, but can't find it. We put mint in the line and pressurized it no luck, same with smoke. All accessible joints have been soap tested yesterday. We have started make some hand size holes in the walls to try to find the leak.

I need to have this fixed and pass inspection. Are there any tricks or techniques that can be used to find the leak?

 

[Doherty Plumbing]

Ok wait I'm confused.

How are you putting 5 PSI into a drainage system with the p-traps installed? Usually the DWV is tested and inspected at "rough-in" stage which doesn't include p-traps being installed yet...

2nd of all what are you using to plug off the drainage system on the vents and sanitary building drain?

 

[Sponsor]

 

[Shacko]

I'm as confused as the other post, how are you sealing the toilet and traps? Why are you using air instead of water? (water shows leaks easier than air), you're not trying to do a smoke test and adding pressure to the lines, are you?, need a lot more information.

 

[tconner]

We did the rough in test and passed inspection a few months ago. as we are finishing, we need to do a low pressure test 1/2" water air test. The test our inspector does is to disconnect the drain from one of the p traps and blow air thru a hose to the other side of the loop seal. He has a pressure gauge hooked up a looks to make sure it holds against all the toilets and traps. It was holding fine about a week ago. (we tested after each toilet was set to make sure it had a good seat.

When we no longer could pass we pulled the toilets and the p-traps one at a time and plugged them. Our assumption was that one of the them had a leak. after we got all of the pulled and still wouldn't hold we figgured that we got a nail or screw from the finish carpenters. We split the DWV system in half (north side/ South side). The south side would not hold. The vents and drains were then all plugged with inflatble plugs or test caps. we pressed the system up 5 psi sowe could hear a leak - no luck. then put mint in the line and pressed up to see if we could smell it. no luck 'cept when we vent the pressure off.


I took pictures of the walls before drywall so we know where every pipe is. The next step is to start cutting apart sections of the south side, plugging the cut and testing both ways to find the bad section. that means alot of holes and a lot more joints. Unless there is a better way.


The house has 6 toilets, 3 on second floor, 2 on first floor and 1 in bsmt, 5 tubs, 3 on 2nd, 1 on 1st and 1 bsmt, 10 sinks between the 3 floors and one rough in wet bar. the north side (includes the entire second floor) seems to be fine. We found that by cutting the main waste line and spliting out the vents.

 

[Doherty Plumbing]

Wow I have never even heard of an inspector actually making someone do a final test on a house. Usually they just walk in, look around and say "great see ya later".

As for a better way....

Hire someone with a camera and have them come scope the lines to see if you have a screw or something inside the piping. If you do then use the locator (used with the camera system) to locate where it is and fix it.

Thats what I would do anyway.

 

[Leejosepho]

over about an hour we lost 1/2 psi.

Somebody needs to tell that inspector to go get a job!

Are you sure nobody bumped the guage during that hour?

 

[tconner]

Here is the required inspection from the county.

FINAL PLUMBING INSPECTION: shall be made after installation of all plumbing equipment and while under final air test.

Basically they shove a hose with a ounces per square inch guage o it and push it thru the p trap. They blow into it until the gauge registers and the level in the p trap goes up an inch or so. Then inspect.

thanks for your help

 

[Nukeman]

So did he do the inspection and you failed? Or are you just pre-testing? More than an inch or two of water worth of pressure will blow out the p-traps, so it could fail if the pressure was too high. The other possibility could be a p-trap that was not completely full (double check every floor drain, shower, sink/lav, washer standpipe, etc.). One would think that if his low pressure test would fail, you would see some kind of leak at one of the p-traps or could be a bad wax ring or something like that.

With the air test, some of the pressure change can be due to temperature changes in the air/pipes while doing the test. I would plug everything up and try a water test and see if you can find the leak.

 

[hj]

Fill the system with water. If it is that small of a leak, you are NOT going to flood the place, but it will eventually show up, since it is unlikely to be under the floor. IF they had that requirement here, EVERY job would cost at least a $1,000.00 more.

 

[Cacher_Chick]

I think the standard the inspector is attempting to comply with needs to be verified.

Here, the final test with water in the traps must hold a pressure of 1" of water column using a manometer.
One PSI is equal to 27.7" of water column.

 

[gage]

Leak source?

Is the ounce gauge falling or the water height dropping or both?

 

[Jimbo]

1/2 PSI is around a foot of water, or as cacher computed, 13.85" water column. That will move water in traps. It could cause a fixture to overflow. Are you using a gauge sufficiently accurate and with sufficient resolution to verify that 1/2 psi pressure??

 

[Hackney plumbing]

I think you may be testing for too long. Thats ALOT of pipe in different temperture zones. if the pipe cools off the pressure will drop....if the pipe heats up the pressure will increase in a closed system.

I'd test it for 5 minutes and call it good. Thats a very sensitive test.

I know i wouldn't tear my house up until the inspector failed it........I really suggest calling the inspector over and have him test it for you. Its cheaper to fail an inspection than to tear the walls out of the house.

 

[Hackney plumbing]

Well I just looked at the original posting date......I assume he figured it out. LOL

 

[Earl Simpson]

I realize this is an old thread but wanted to make some comments.
I think this test is to be done before all the fixtures are installed and if the builder is expecting a pencil whip he may skip this test and hope he doesn't get caught. Thank God for inspectors that actually inspect stuff. My roughed in plumbing was pencil whipped and now I can't get any info on what is actually under the slab. They have a code violation with a 3" pipe and not 4". 4 non standard bathrooms and 4 toilets/42 fixture count. In addition they ran a 3" waste pipe 10-15' "at least" away from the septic tank before doing a something under the dirt to point it in the opposite direction.
Everything that was signed off was covered with dirt. Builders want to hide stuff and do a cheap job if they can get away with it. I am sorry I ever picked this builder as I told him at the beginning I needed 4" pipe. Even offered to pay extra to do things right but was told their way only.

That is why we need honest inspectors as most of us do not live next to the construction site. Thanks to all plumbers that do the right thing.

 

[Kreemoweet]

?! Pressure test at final, after the pipes are all covered up, makes no sense whatever. Air test is bad in any event.

 

[Jadnashua]

IF the wallboard was installed, a screw or nail into a drain pipe might not leak much, but it could cause the pressure to drop.

 

[Terry]

In Washington State, there is a rough-in inspection with either an air or a water test. Normally without any p-traps installed.
At finish they check to see if everything is installed correctly. We don't have an air test on installed fixtures.
I can't imagine why anyone would.

Very brief statements from the book below.

UPC 712.2 Water Test
Openings should be tightly plugged except the highest opening.
Tested for at least 15 minutes with ten feet of head except where the uppermost pipes don't reach that high.

UPC 712.3 Air Test
5 PSI for 15 minutes

I don't see a method in UPC for testing after that.