Venting through a cathedral ceiling
Posted by Ed Breyer on June 26, 2002 at 23:14:05:
I�m plumbing a bathroom in my new addition and have a question regarding proper venting. Let me start by saying I have extensive plumbing experience (for a non-professional) along with the local code info for proper DWV diameter and critical vent distances but I�ve just never faced this particular issue:

The 3� toilet line and associated vent stack in my new bathroom will run through the west wall of the room then up inside the sloped cavity of the room�s vaulted ceiling before projecting through the sloped roof (on the west side of and a couple feet below the roof ridge). The bathtub, which is on the opposite side of the room will need to tie into that vent line because I don't want a vent pipe on the front side of the house. I envision two possibilities for dealing with the room�s vaulted ceiling:

1) Use a vent loop for the bathtub which will travel under the bathroom floor and tie into the vent stack at the appropriate height in the west wall.

2) Run the bathtub vent line up the east wall and sloped cavity of the room�s vaulted ceiling, under the ridge beam (the ceiling is furred down and flat under the peak) and then back down the other sloped ceiling for about two feet where it will then connect to the 3� vent stack just before the stack exits the roof.

My framing contractor - who readily admits he has no plumbing experience - expressed concern over the bathtub vent line running �downhill� before tying into the main vent stack. However, since any water getting into it would certainly drain out properly, I can see no reason why solution #2 wouldn�t work.

Any ideas or preferences?

By the way � I haven�t asked the inspector�s advice because 1) she is brand new and has no plumbing experience and 2) I�m afraid she will think I have no clue and get very picky on the inspection.

Thanks in advance!


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