p trap question ---

[fsteyer]

I'm doing a bathroom remodel and the (planned) sink wall has no room to run the p trap into. Can a p trap drain down (after a short horizontal run). I guess my question is: does the UPC sepicify how long the horizontal run after a p trap has to be . ( I know, I know .... I still have the vent question .. but my brain can only handle one item at a time :mrgreen: )
Thanks

[dhill]

Are you trying to put the p-trap inside the wall or outside the wall under the cabinet. Think about what the purpose of the p-trap is, and use common sense to determine if what you're trying to do will work. I'm not sure I have a clear picture of what you're attempting to do. The horizontal run on a p-trap shouldn't make much difference in how the trap works, as long as the trap is low enough to sufficiently trap the water so that gases can't pass through it.

[fsteyer]

Thank for the reply -

instead of having the drain pipe (after the trap go) into the wall and then down(or whatever) I'd like to bring the drain pipe (after the trap) down into the floor (joists) just ahead of the wall. Or, as I have seen in the past, have the trap make a complete (vertical) loop and then the pipe went straight down into the floor. So my question is if the UPC allows for that or not.
Thanks again ...

[bkrahmer]

I don't think there is a minimum length of horizontal run after the trap, but what are you going to do about your vent?

[VALENT]

yes that is allowed but you will be using an s-trap

[bkrahmer]

I ended up with a bathroom wall that sits directly above the floor joist. So, I ran my pipe through the floor instead. At first, I had an S-trap arrangement, but my inspector wouldn't allow it. What I did was to put a tee in, and go into the wall at a 45 for the vent. If you want a quick and for-sure answer, call your plumbing inspector. He may or may not allow an s-trap.

[VALENT]

I really dont know if a remodel would allow a vent stack to be added but I guess it would depend on the specifics of this particular remodel.

[Tom R]

Yeah, - - I know S-traps aren't allowed out my way.

[fsteyer]

thanks guys -

I'll check the dimensions for an s trap.

this bathroom will be in the 2nd floor so the vent can be run to the attic an connect to the main stack. I can go up in the wall but not down or sideways.

Thanks again ...

ps. this would be much easier if my regular plumber wouldn't be on vacation. The nerve of the guy! :lol:

[bkrahmer]

Here's a sketch of what I did. I recommend going this route if you have the room. You won't have to second guess yourself this way.

[fsteyer]

Thanks for that confirmation ... thats what I sort of had in mind.

[Sparks]

I don't believe s-traps are allowed anywhere (anywhere that has`regulations).

[Sparks]

Ok, I dug out my book. S-traps not allowed by either the IRC or UPC. Also trap arm to vent distance must be more than 2 times trap diameter, so usually 3" min. That's if your vent is close by. Maybe you could use a vertcal leg waste fixture drain. You would have a trap, an horizontal 8" trap arm, an elbow going down to where you need to be then upsizing your pipe one size from there, then horizontal to your main soil stack,this would be legal per IRC and UPC. Just don't exceed maximum trap arm runs to vent. UPC says 3' 6" for 1.5 and 5' for 2". What you were describing was indeed an s-trap and this would be prohibited.

[VALENT]

I wonder why s-traps are not allowed as in reality they are the same thing in less space as a p-trap and then the portion inside the wall-except no vent.

[bkrahmer]

S-traps are not allowed because they have a tendency to get siphoned dry. Sewer gas, yum...

[VALENT]

thanks bkrahmer

[Sparks]

Exactly, water filling the downstream vertical portion of the s-trap will cause siphoning and loss of trap seals. Trap seals (water seal) must be maintained to prevent sewer gases from entering the dwelling. The vertical-leg fixture drain that I mentioned is not technically a s-trap because it has a horizontal arm and an increased size in the vertical drain preventing the siphoning.

[fsteyer]

thanks for all the great info guys. I'm just curious why, if s traps aren't allowed everypone sells them? Just curious ...
thanks

[Sparks]

You'll find they sell alot of things that are not allowed in regard to plumbing and electrical, I don't know why either. Good question.