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Author:
Temu Chechu (MN)
Hi,
Thanks in advance for your answer. I'm confused about wet venting. My understanding is that it is allowed for a bathroom group. Each drainpipe must be increased by one pipe size and there is one vent (lav) that vents all the fixtures (shower/tub, lav, toilet)
Normally a lav needs 1/1/4 drain so that is increased to 1.5 inch drain.
Normally a toilet needs a 3 inch drain so that is increase to 4 inch.
Normally a shower along (not a tub) needs a 2 inch drain. So I guess it would need to be increased to 2.5 inches which doesn't really exist so it would need to be increased to 3 inches?
Is this true and if so when does it need to go from 2 inches to 3 inches? The shower drain is 2 inches. Does it need to increase right away on the tailpiece?
Also, if I recall the pipes need to connect in a specific order?
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Author:
packy (MA)
only the piping that is acting as a vent/drain combo needs to be increased in size.
the shower vent would normally be 1 1/2 inch so it gets increased to 2 inch.
that 2 inch then accepts the lav drain which is 1 1/2 inch.
the toilet does not act as a vent in any way so it stays 3 inch.
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Author:
steve (CA)
Some codes require the toilet to be the most downstream fixture. The drains for the wet vented fixtures enter the horizontal drain pipe from a horizontal direction and the vent connection enters the horizontal drain pipe from a vertical direction. Some codes require the toilet to have a 2" minimum vent size, so if you are using the sink drain as the vent for the wet vented fixtures, the dry vent above the sink drain would also need to be 2". Check what your local codes requires. Often times the local building department has paper/online "handouts" with common code items for kitchen or bath remodels.
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Author:
brucezh (MI)
You're right that wet venting is allowed for a bathroom group, and each drainpipe typically needs to be increased by one size. For example, the lav’s 1 1/4-inch drain would be increased to 1.5 inches, and the toilet's 3-inch drain stays at 3 inches unless local codes require 4 inches. For the shower, since 2.5 inches doesn’t exist, it would be increased to 3 inches. As for when the shower drain needs to increase, it usually happens before the drain connects to the main stack, but it’s always good to double-check with local codes.
Edited 1 times.
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