Best way to vent a bathroom following IRC

Old 07-01-21, 05:40 PM
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Best way to vent a bathroom following IRC

Have a bathroom group with Water Closet, Lav, Shower and a tub what is the best way to vent these 4 fixtures. Currently there is a 4 inch line stubbed into the foundation, I would take a vent off before each ptrap for the tub shower and one off the lav and toilet and vent them all through the roof but it seems there should be a better way. Thanks


Last edited by PJmax; 07-01-21 at 06:11 PM. Reason: resized pic
Old 07-01-21, 06:19 PM
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I'd make the following changes:

1) Connect the tub to the lateral 'after' the sink. This allows it to use the sink as a wet vent. Tub 1.5" pipe. No vent required.
2) Shower is good. Use 2" pipe. No vent required as it's using the sink vent.
3) Sink uses 1.5" pipe and 1.5" vent. Sink always needs a vent.
4) Toilet uses 3" pipe off the main lateral. Wye off to a 2" vent.

Use wyes or combo wyes for all connections, no San Tees - except for the vanity popping out of the wall.

Do you already have a vent through the roof for the drain system as a whole?

Vents can back-vent (tie together) into the 2" pipe in the attic so you only have one roof penetration.

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