Hello,
I want to install a sink in a gazebo on my deck. The 2" drain line will run straight down from the sink then turn 90 deg and run horizontally (sloped 1/2" per ft) into my crawlspace about 15 ft away. The p-trap and vent line (AAV) I want to locate in my crawlspace so it doesn't freeze. Is it feasible to locate a p-trap this far horizontally from a sink?

Thanks,
Tom

You would have to consult your local plumbing code office to determine if what you wish to do is permissible.

The remote distance from the sink and the velocity of water discharging into the trap could cause a siphoning effect of the trap rendering it useless.

That said, locating the trap inside the conditioned space is certainly one way to keep the trap from freezing, but it does not address the freezing of the water supply pipes for this exterior sink location.

Personally, I would install the trap and vent at the remote location at the sink, then simply add antifreeze to the trap (or remove it) in the winter to keep it from freezing.

Manhatten presents good info, but I'd definitely recommend that you install the PTRAP and the AAV outside... right under the sink is best. Here, the only issue would be the PTRAP and the water lines... the AAV can't freeze. In freezing conditions you'll drain the water lines anyway, so as suggested by Manhatten, that would be the time to deposit some antifreeze or a cooking oil (better choice here) into the trap and wait until the thaw.

Be sure to pitch your water pipes so they drain back to a shutoff with a drain or a shutoff and a boiler drain of some kind.

The pitch required for this installation is 1/4" per foot and the pipe only needs to 1.5"... unless you are installing a disposal... then 2" is good here.

Back to you...

Mark

Installing the trap and vent near the sink seems like a better solution than what I was thinking of. Thanks both of you for the advice.

Suggest P trap with drain plug. Then you can drain trap when you shut off water for the winter.


https://www.askmehelpdesk.com/members/hkstroud-albums-+pictures-picture520-trap-drain.jpg

If it is bar sink than you can even run water to your garden and use it for irrigation... no trap necessary here at all...

Why wouldn't you want to put P-trap under the sink ? No space ? Eye sore ?