Double p-trap?

John Stephenson · 05-30-2007, 10:00 AM

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Richard Moore · 05-30-2007, 11:05 AM

What you have there is more like an S-trap than a double P. Anyway, it's wrong. The trap arm (1st horizontal bit after the trap) should be horizontal all the way to the wall. They need to get a longer tail-piece (vertical bit) and get rid of the last two 90's. Looks like they will have to move or modify the shelf to do it properly.

Anthony Alderman · 05-30-2007, 11:09 AM

It's definitely not pretty but I believe that the horizontal run is enough to break any siphoning seal. probably wouldn't be code though.

Tony

**Rick Cantrell** · 05-30-2007, 03:39 PM

Richard is correct.
The trap arm should be at least 8" long.
Better thought to lower the trap and do away with the 90's then go straight into the waste pipe.

**brian schmitt** · 05-31-2007, 02:14 PM

rick,
section 1002.2 of the u.p.c., length of trap arm = 2x the diameter of the trap arm minimum

Joshua Hardesty · 06-01-2007, 06:43 PM

That's an S-trap. If it was a double P-trap, there'd be a second place where water sat.

Drains are alowed to slope to 1/2 of the pipe diameter before reaching a vent. That looks to be about 3 times the diameter.

Brian: I believe that code's referring to crown vents, right? But again, there's no vent in that picture so I'm not sure if that specifically applies.

What I don't get is why all these plumbers have those 90's and not extensions. I use extensions all the time to fix problems like that. You know how many 90's I keep stocked? NONE.

David R2 · 06-10-2007, 11:56 AM

The P trap has to be lower. Than the arm goes straight out (or with a minor slope) into the wall, where it connects to a vent and a drain. If you cannot lower the P trap, you can add a vent (AAV) to the arm right where that 90 degree bend is. Allowed in most places.

Before any drain goes vertical (downhill) it has to be vented. Otherwise the P trap is now a long S shape, and that will suck its seal water out occasionally when it drains.

David

**brian schmitt** · 06-11-2007, 11:06 AM

joshua,
crown venting is not approved by code. the section and code reference is for all legally reconized traps!

Joshua Hardesty · 06-11-2007, 08:39 PM

Originally Posted by brian schmitt

joshua,
crown venting is not approved by code. the section and code reference is for all legally reconized traps!

Indeed, I was just saying that anything shorter than 2x the diameter of the pipe is considered a crown vent, and that the length of the arm is definately longer than 2x the diameter before it reaches a vent.