Not an S Trap?

[OZ324]

The access hole in this new vanity is higher than the rough-in drain. See pic. Modifying the vanity isn't the problem. I'd like to avoid having the trap go below the bottom shelf. Can I put a 45 on the drain and run up the outside of the wall or is that basically creating an S trap? Hope this makes sense.

 

[Terry]

The trap arm needs to come out straight without changes of direction upward.

 

[Sponsor]

 

[OZ324]

The trap arm needs to come out straight without changes of direction upward.

Well darn. So my trap needs to go below the shelf huh?

 

[OZ324]

Feel dumb asking, but Is this also an S trap?

 

[Jeff H Young]

Well thats how I had an inspector call it years ago he said that is basicaly an s trap , I think its an improper use of words but neverthe less totaly not code to do that Sorry to say.
Some might say to go ahead offset the trap arm and install an AAV under sink thats a way that works and usualy meets code especialy IPC code . Im not so sure it would be UPC legal though.

 

[wwhitney]

Feel dumb asking, but Is this also an S trap?

Yes, it is.

The rule for P-traps is this:

The "trap weir" is the height of water where, if the trap is empty and you start dribbling water into the sink, water would first spill out of the u-bend into the rest of the drain system.

The "top of air" (a term I just made up) is the height of water at which, if you plugged the vertical sink drain in the wall and slowly filled up the system, the air space in the sink drain outside the wall would become separated by the water from the airspace in the vertical vent pipe (not shown in your drawing)

And the rule is that the top of air has to be higher than the trap weir. Otherwise, if the drain pipe outside the wall fills up with water, the trap can siphon.

Cheers, Wayne

 

[Jeff H Young]

not legal amy way you slice it

 

[OZ324]

Thanks to all. Gonna modify the vanity so the trap falls below the bottom shelf. Not ideal, but will meet code and be done right.