Horizontal section of vent stack

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Hi - homeowner here trying to figure out plumbing for the addition I'm putting on my home. I've been reading about venting, and see that typically there is a vent stack that goes straight up. In my case, I can't go up where my line comes in (fireplace above it), so I'd have to run horizontal for ~8 feet to go up in a wall. Please look over the attached diagram to see if my plan will work. I'm in central Pennsylvania if that makes any difference as for code.

There are a few questions I have:
Is the horizontal section (pitched 1/4" per foot) of vent pipe acceptable?

Is there a requirement for height of my laundry drain (elevation above where the drain line comes into building)?

Does the laundry drain need a separate vent?

How high should the vent stick out above roof? Is 18 inches above roof acceptable?

Thanks for your help!
Joel

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teststrips

Anyone? Hoping mainly to find out if the horizontal section of the vent stack is ok.

Missouri Bound

Your horizontal pitch is fine. mY only concern would be the height of the laundry stand pipe. The stand pipe is generally 36" from the bottom of the washer. What will that leave you with?

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I just looked at my current setup again. I was thinking the washer hose was up near the ceiling - instead it goes in about 50 inches off the floor, and there is a vent? that sticks up a little higher + terminates into thin air (see picture).

I also checked the current septic outlet height which is 42 above the floor, so I guess 8 inches of separation has been working fine for the 5 years I've owned the house. Only difference I see is that the current system is about 25 feet away from the drain, and it'll only be 5 or so feet away in its new home.

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