sewer vent size??

[jahyde]

So I know in general home construction 1.5" vents are mandated for a 3" drain.... But trying to keep vent sizes slim in my trailer, how many people have used 1 1/4 on the black tank?

[Redneck Teepee]

Your not getting it inspected so use what will fit in your space and call it good. 1-1/4" is plenty big
Not sure what the I.D. of your wall or chase is but a 1-1/2" ABS/PVC vent pipe will measure 1-7/8" +/- O.D....1-1/4 will be 1-5/8" +/- O.D.

[MtnDon]

I used a 1" line from holding tank up to the roof vent where I adapted up to whatever size the RV roof vent needed. The tank fills and drains fine.

[satch]

Your not getting it inspected so use what will fit in your space and call it good. 1-1/4" is plenty big
Not sure what the I.D. of your wall or chase is but a 1-1/2" ABS/PVC vent pipe will measure 1-7/8" +/- O.D....1-1/4 will be 1-5/8" +/- O.D.

Agreed, The vent pipe is meant to equalize the pressure of flow, so using a smaller vent just means draining might take a little longer. No big deal.

[jahyde]

thanks... that makes me feel a bit better, I have worked a lot in home construction, and some associates even said "has to be 1.5", but I had a feeling it would breath just as well on 1".

[Dale M.]

Its just air and if there is very little resistance to flow, might get away with as little as 1/2 id tubing/pipe...

Dale

[Pleiades]

Plumber here. . I have witnessed 3/8 inch copper line give enough air to flush a house toilet. So 1inch or probably be sufficient