Double Trapped?

Morning all.

Wrote this up as double-trapped but now I am having my doubts if it’s an issue.

Any input would be appreciated.


And after reading the Illinois plumbing Code and talking with the local code enforcement officer, I now know I made a bad call.

Luckily, I never got in a argument with the builder! :slight_smile:

Double trap is when the fixture drains through 2 traps in series. I don’t see anyting wrong in your photo.

I looked at the trap in the rear and could see a possibility, however remote, that water flowing from the garbage disposal could suck the second trap dry.

But you are correct and I will explain that to my client this morning at his final walk-through.

Thanks for the input.

That set-up is allowed by the IRC, but prohibited by the UPC. It would not be allowed in my State, not because it’s a “double trap” (it’s not), but because two traps cannot share the same trap-arm under UPC requirements.

Thanks Jeff.

I was just reading a discussion you had had about this on a plumbing board.

Very informative and I have since updated my notes so I won’t refer to this as a double-trap anymore. Since, it’s not. Accuracy is important! :cool:

If that’s the thread I’m thinking of, I got hammered for several days before the “verdict” came in.

Yep. You did.

Wish I had read it BEFORE I sent out the report though.

All good though. Final walk-through today so I’ll explain my bad call while I am there. :neutral:

That’s fine, Jeff.

BTW: did you know that draining a dishwasher through a garbage disposer is not allowed in the Illinois Plumbing Code? I found that out recently.

Jeff, that’s good info.
Would you please site the sections for both the UPC and IRC where this issue is covered?

Lots of interesting things in the Illinois Plumbing Code.

Here’s what you referred to though.

Section 890.770 Dishwashing Machines

a) Domestic Dishwasher (Private Residence). When a domestic dishwashing machine drain line is connected to the house side of a trap from a sink, the drain from the dishwasher shall be carried up to the underside of the spill rim of the sink. Dishwashing machines shall discharge separately into a trap or tail piece of the kitchen sink and shall not connect to the food waste disposal unit.

UPC 1001.1 Each plumbing fixture, excepting those having integral traps or as permitted in Section 1001.2, shall be separately trapped by an approved type waterseal trap. Not more than one (1) trap shall be permitted on a trap arm.

The IPC references are 908.1 & 908.2. I don’t have the IPC handy, but I’ll post it when I get back in the office. . .

IPC 908.1 Individual vent as common vent. An individual vent is permitted to vent two traps or trapped fixtures as a common vent. The traps or trapped fixtures being common vented shall be located on the same floor level.

IPC 908.2 Connection at the same level. Where the fixture drains being common vented connect at the same level, the vent connection shall be at the interconnection of the fixture drains or downstream of the interconnection.