Minimum Trap Arm Length

handyman923 · May 30, 2013

Is there a minimum trap arm length for a washer stand pipe? Right now, I have the outlet from the P-trap butting tight to the sanitary tee. Is this too close? Will this create a S trap?

Thanks for any advice!

Jadnashua · May 30, 2013

I think I read two pipe diameters, but don't quote me on this...

Sponsor · 2022-01-29T12:20:58-0800

hj · May 30, 2013

trap

Depending on how you measure the trap arm, the two fittings may "force" it to be at least two diameters between the "pipes". IF you have a proper vent you cannot "create" an "S" trap as long as the maximum length is within the parameters for the pipe size.

denikar · May 31, 2013

This

http://inspectapedia.com/plumbing/1623s.jpg

Comes to mind.

WJcandee · May 31, 2013

The third page of this pdf has a diagram and a table that may be helpful. You measure, according to it, from the interior portion of the vertical pipe on the p-trap (the weir is where it tips over to the horizontal) TO the closest portion of the vent pipe. The top right diagram on the third page of the document makes it clearer. 3" pipe has a minimum 6" trap arm.

Plumbing-and-Trenching-for-Homeowners---2018 (klickitatcounty.org)

MikePlummer · Jun 1, 2013

our code requires a minimum of 2 pipe diam to avoid crown venting

Minimum Trap Arm Length

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