I have a 2" vent line I need to pass up to the attic, then tie to the 3" main vent a few feet away inside the attic.

Not difficult to do I can manage.

The problem is I need to cut a hole through the top plate to fit the 2" pipe through.

The wall is not load bearing, still I prefer not to notch too much of it.

The top plate consists of a double 2x4, so I would have to drill the hole from below, then go up to the attic to drill down and hope they perfectly align.

I have hole saws size 2.5" and 3". 2.5" seem like it would work, but very tight. Further it will not pass a 2" coupling, not that I would have one there. But I am thinking if I end up not drilling the plates perfectly through both 2x4s, there is no tolerance or room for error, plus I need to push the 2" pipe through the hole up high in the attiic so I can get the bottom of it above the middle plate and feed that through a hole I will drill there.

A 3" hole will work but take too much materials out of the 2x4s.

What size hole saws you all use for 2" PVC pipes?

2.5" OK to take a chance, or should I go buy a 2-5/8" or 2-3/4" hole saw?

2 9/16" works for the pipe diameter, not sure what will work if you need to slip a coupling thru.

[www.grainger.com]



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First drill a 1/4" hole all the way through the plate as a pilot hole. Then use the 2 1/2" hole saw centered with the pilot hole from both sides. The hole will be straight and there will be 1/8" clearance for the pipe. There should be no reason to ever slide a coupling through the hole.

DITTO

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

i typically use a 3 1/8 bit....you can use a 2 9/16 and the pipe will be fairly tight....you wont fit a fitting there though unless you use a 3 1/8"

If you get into a situation where the hole has to be "fire stopped" the smaller hole will work better. I have never even OWNED a 3 1/4" bit.

I use a 2 1/2"

i drill a 2 1/2" hole for 2" pipe. i test the hole by trying to slide one of the red sox bats down it.

quote; i test the hole by trying to slide one of the red sox bats down it

Right now, it may be the only thing it, or a Diamondback's bat, is good for. If I use my own bit it is 2 9/16, but he said he had a 2 1/2" one which is good enough.

I can't use a 3-1/4" hole. The top plate is a 2x4 which is basically 3.5" wide. A 3-1/4" hole basically leave no materials I might as well cut it all the way through and stablize the two top plates some other way.

Seems a 2.5" hole worked.

Sum?could you reductive, reduce and then expand an 1 1/2"pipe at this point????More often than not the lessor tubing passing through a smaller plate is a better option.Yes more money in fitting,s but you leave more wood with no effect to the vent.please do use reducing coupling rather than bushing if you go this route.

Lemon, I already did it with the 2.5" hole.

I thought about reducing to 1.5", however, where the tie in back to the 3" main vent is a vent tee 3x3x2, so I don't want to go from a 2" to a 1.5" only to go through the plates then somewhere change back to 2", something about that bothers me.

It should not. realistic.a re-vent would never be a service point and the air flow reduction is mute.

The top plate consists of a double 2x4, so I would have to drill the hole from below, then go up to the attic to drill down and hope they perfectly align.

Am I missing something?

(Before and after drilling your pilot hole, make sure you're well clear of other utilities and obstructions.)

Just drill from whichever side is easier. After you drill the full depth of the first 2x4, withdraw the hole saw and, if the core isn't stuck in the saw, use a chisel or screwdriver to knock the core out of the 2x4. Put the saw back in the hole and drill the rest of the way through the deeper 2x4.

I've sawed through nails and embedded angle iron with nothing more than a cheap hole saw, so I don't see anything like that getting in the way.

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Links to the State of Wisconsin Plumbing Code:
[docs.legis.wisconsin.gov]
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I am not a plumber.
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jblanche, it's hard to explain, part of it is the motor housing of my drill, if I drilled the first one and remove the core, I could not reach in to drill out the second one. The hole saw "shaft" is very short so I had it bottomed out on the chuck.

In any event it's done now.

The only thing is since the hole is 2.5", the 2" pipe goes through it and once side of it is touching the inside of these two plates. There is no stress that I can tell but it is hugging it tight. It is a vent pipe and not drain, but I do worry if expansion/contraction of the wood may cause problems.

Should I slide a piece of roofing felt around the inside of the hole (outside of the pipe) or doesn't matter?