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Right size drain diameter

Posted by davidro1 (My Page) on
Tue, May 15, 12 at 3:47

Shower drains drain well when 1.5" diameter. The drain pipe there is an "arm" not a branch, so it can go a certain distance (depending on its diameter) before it needs to connect to venting. Then it becomes a branch not an arm.

Same for washing machine drains.

Here is a link that might be useful: Side discussion here, on drain size for washer


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RE: Right size drain diameter

The first step in determining the correct size of drain is to consult the code table that lists all the fixtures and the required minimum trap & drain size.

The code minimum for both a shower & a washing machine is 2" so argue as you might, you are still required to install a 2" drain line for both the fixture arm & the vented branch.


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