Can someone fill me in on the proper plumbing of a floor drain, specifically with regard to the trap arm?
As I understand it, typically permitted trap arm lengths are less than that required in a floor drain. What’s the proper way to deal with this? I’m guessing one uses oversize pipe for the trap arm, but I haven’t been able to find any references giving pipe size vs. distance. Nor am I clear on whether you can reduce the trap arm to connect to a smaller (2″ stack). My contractor (not a plumber) swears you don’t need to vent a floor drain, which I tend to doubt. I’m in Los Angeles, for any of you familiar with the codes here. But I’ll take general advice!
Thanks.
Replies
Talk to the building inspector. LA is pretty tight so far as code goes and I dont know your answer but whatever the inspector says it what goes in LA. FWIW I think it ought to be vented and I think you need a water tap (sp) to keep the trap from drying out.
Bing
.... or a deep seal trap (rather than the expense of a trap primer).
California is adopting the Uniform Plumbing Code (UPC) most of the state goes by the state code which is modeled after the UPC.
Floor drain minimum is 2".
2" drain can have a trap arm up to 5 feet.
If you do not have a wall within 5' you would connect the vent pipe off the trap arm & roll it so the fitting comes off just above the centerline of the trap arm. If this is the path taken then you must use drainage pattern fittings & the pipe must grade atleast 1/4" per foot until the vent is atleast 6" above the flood level of the fixture, then you can reduce the grade & use vent fittings.
A trap primer is also required to keep the trap wet, unless you can get the administrative authority to buy off on a trapguard by Proset¯