Dishwasher Discharge Location

Is it ok for a dishwasher to discharge after the pee-trap?

The pee trap? lol. No, it’s not.

The dishwasher drain must be connected beforethe P-trap, if it is installed after the P-trap sewer gases have the potentialto come back in to the dishwasher.

As long as there is a high loop it does not matter where its connected. Looks to me like that drain line needs to be tied off a little higher. No sewer gas the drain line stays full of water. :wink:

P2717.2 Sink and Dishwasher

The combined discharge from a dishwasher and a one- or two-compartment sink, with or without a food-waste disposer, shall be served by a trap of not less than 11/2 inches (38 mm) in outside diameter. The dishwasher discharge pipe or tubing shall rise to the underside of the counter and be fastened or otherwise held in that position before connecting to the head of the food-waste disposer or to a wye fitting in the sink tailpiece.

There is also one that states do not double trap which is correct???

I guess, this would be one instance that the Code is telling you to double trap and it is OK. Huh! :wink:

Hope all is good Charley.

Marcel… that DW drain line IS attached to the tailpiece. The tailpiece is simply installed in the wrong location! :shock:

So when it is installed in the right place, like Charley pointed out, you got a double trap. The pee trap and the high loop which technically acts like another trap. :slight_smile:

i’ll try & decipher
it’s not dbl trapped if it discharges to the atmospheric (tailpipe) side of the p-trap

i’ll try & decipher
it’s not dbl trapped if it discharges to the open atmospheric (tailpipe) side of the p-trap
& downstream of the p-trap creates a cross contamination potential
most dw/disposal install instructions have this or similar


Thanks Barry, I forgot about the atmospheric discharge when connected to the tail piece in the right place.
I had my mind on the p-trap.

understood, McHammer

now comes the big question, are those tailpipe wyes even approved?

a lot of the non-pvc aftermarket under sink/lav plmg i see isn’t marked, yet we see it in almost every property we inspect even new const

P2609.1 Identification
Each length of pipe and each pipe fitting, trap, fixture, material and device utilized in a plumbing system shall bear the identification of the manufacturer and any markings required by the applicable referenced standards. Nipples created from the cutting and threading of approved pipe shall not be required to be identified.

Exception: Where the manufacturer identification cannot be marked on pipe fittings and pipe nipples because of the small size of such fittings, the identification shall be printed on the item packaging or on documentation provided with the item.

They sell those at the big box stores and I haven’t seen marks on them yet. :slight_smile:

there’s a lot of imported crap sold
little meets approval by the letter of the code & polypropylene isn’t on any list i’ve seen, yet the ahj allows
i just leave a canned comment in the dwv report section & seldom have to redact when i find approved material

I’m thinking that old man from Texas has it…

Yup. :slight_smile: