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Arky217 10-05-2012 12:55 AM

minimum drain size for tub/shower and for sink
 
If a sink or a tub/shower has a 1.5" tailpiece, is there any advantage to having it drain into a 2" pipe rather than just keeping the drain pipe the same 1.5" size as the tailpiece ?

Thanks,
Arky

TheEplumber 10-05-2012 01:12 AM

Quote:

Originally Posted by Arky217 (Post 1024093)
If a sink or a tub/shower has a 1.5" tailpiece, is there any advantage to having it drain into a 2" pipe rather than just keeping the drain pipe the same 1.5" size as the tailpiece ?

Thanks,
Arky

No big advantage but it won't hurt either.
My state does not allow 1.5" pipe under a slab, so all our basement tubs and lavs are piped 2".

md2lgyk 10-05-2012 08:17 AM

Quote:

Originally Posted by TheEplumber (Post 1024097)
My state does not allow 1.5" pipe under a slab, so all our basement tubs and lavs are piped 2".

Do you know the basis for this rule? Just curious.

TheEplumber 10-05-2012 11:10 AM

Quote:

Originally Posted by md2lgyk (Post 1024196)
Do you know the basis for this rule? Just curious.

No, not really. I started plumbing here in the mid 80's and that rule was in place then too. I have been told that since 1.5" is used mostly on lavs and tubs, it is upsized to avoid blockage as it is not accessible (under slab) to repair. But thats not an official response. The rule holds for venting under slab too.
Here's another one- regardless of the fixture load on the building drain, I must stub 4" out of the building with a 4" clean out.
You can tell when a Washington plumber crosses the border for work- they sometimes forget these rules.:laughing:
We work off UPC and are in the process of adopting IPC (Idaho Plumbing Code) It too is adopted from UPC. but has several venting modifications- or so I'm told. I haven't read it yet :whistling2:


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