Thread: Capped plumbing vents, New construction

Have never encountered this before. Inspection on new construction, the two plumbing vents on the roof were capped. I was looking forward to running the water inside and watching how it was going to drain. There was a mechanical vent in the kitchen island, and one in the garage by the boiler and hot water storage tank (not sure what that one was venting.) Well to my surprise everything drained great, and I used lots and lots of water, including a big jacuzzi tub. I though maybe there might be some mechanical vents in the attic, but the venting system was normal, except that it was all 4" PVC until it went through the roof. Why is the plumbing draining OK, I am baffled.Is it because of the 4" PVC in the attic, even though its capped off??

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The caps must be there to keep rain out

I'd bet they were put in place to pressure test the system and the plumber forgot to remove them. Venting is kind of a mystical thing sometimes. I've seen things drain okay with no venting whatsoever. At least visually it's okay. You never know if the traps are getting sucked dry. And, sometimes you'll hear all kinds of funny sounds when everything looks okay.

In any case, the builder should remove them.

Caps should not be sealing plumbing vents and exposed to weather PVC piping should be painted to help protect it from untraviolet sun rays.

Did you give them a twist?

Paul hit it. They are capped when the system is pressure tested.

Yes Wayne, I tried to get them off but they were glued.

Plumber probably didn't get his last full check. That's why he 'forgot' to cut them off.

I see them sometimes where someone has just whacked them with a hammer to open them up. Not all that clean of a job.

Something similar happened to me about 6 years ago. I was inspecting a 10 year old house built on a hillside. Couldn't get my ladder up to the roof, but from the ground I could see a cap was still on a vent.

Seller was explaining to the buyer the radon system she had installed when she bought the house. I explained it was installed wrong, the fan was in the basement, but no, she insisted she only hires the best to work on her house. Lo & behold, the radon came back at just over 16; they never removed the cap. While she thought she was safe, she wasn't. I don't know if she sued or not.

They may also be there to keep the A$$hole construction workers from dumping crap down the vent lines. I have had to cut open systems several times to remove all kinds of stuff. Wood, bundles of stiff wires that are used to hold batt insulation in place, smaller pipe etc. Not sure why they do that but a knock-out glue cap usually keeps them out. They should be removed on final/finish.

Would that rubber boot flashing fit over that cap without tearing?

If not, that would indicate that the pipe was capped *AFTER* the roof was installed.