I'm roughing in the plumbing for my two story house before pouring the slab.
The downstairs bathroom will have a toilet, laundry sink, clothes washer
drain and shower. Everything drains to the 3" main under the slab.
Question: Can I combine the laundry sink 2" drain, with the clothes washer
drain shower drain or should it have it's own 2" pipe going to the 3"?
According to my copy of Code Check from a few years ago:
Under the UPC, clothes washers count as 2 fixture units, showers as 3
fixture units, and laundry tubs as 2 fixture units. A horizontal 2"
drain can handle 8 fixture units. So you could drain all three with a
single 2" line. Of course, everything has to be properly vented.
Under the IRC, the 2" horizontal drain can only handle 6 fixture
units, but the shower only counts as 2 fixture units, so the 2"
horizontal line is still OK.
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