kitchen sink disposal drain trap problem

mystic_cobra

I am installing a new disposal under a new sink to an old waste drain. The drain is metal. It looks like cast iron, but might just be thick copper. House was built in 1965.

The new single sink is deeper so the disposal sits lower. I have the correct connections via the trap and disposal exhaust but my pipes don't line up. The exhaust from the disposal is nearly at the same level as the drain pipe. Once I connect the trap to the waste pipe, the top of the trap is now too high for the exhaust from the disposal.

The kid at home depot says you cannot extend the down stream side of the trap which would lower the trap but allow the exhaust from the disposal to connect easily. Instead he suggested a pair of form-a-fit tailpieces to make the connections. I think this is a jack job but I think it will make the connections.

How should I handle this? Is this a common issue?

mystic_cobra

mock up of connections without straight exhaust pipe from disposal.

ben's plumbing

please don't even think of doing it that way...

mystic_cobra

Yeah, I know that's ridiculous. I might do it until I can get to a real plumbing supply store on Monday as we need the sink this weekend.

I'd like to extend the wall drain pipe down and just lower my trap if an extension pipe exists and its legal for code. This seems the cleanest.

ben's plumbing

ok you made me fell much better you know what your doing about lowering the drain to do it right....yea if you need sink go for it let us know how it works.....

mystic_cobra

So, can I connect a pipe (or series of pipes) to fix this and have it pass code without opening the wall to lower the drain pipe?

ben's plumbing

no you have to cut wall to lower piping to accept drain ...you can't elbow existing drain down...if thats what your thinking..sorry... keep in mind there should be a vent there as well

mystic_cobra

I'm assuming the vent is at the top of the waste pipe. The sink was here previously. I'm not sure why you mention that.

This sucks.

ben's plumbing

you have to cut wall open ..cut copper drain intall tee or wye which ever will fit best... i like wye use fernco couplings set drain to accept drain from disposal... I mention vent because if you were to just elbow down drain comming out of wall and installing disposal drain with trap you would be double trapping ...which would affect vent

mystic_cobra

Ah, now it makes sense.

Double tap = good.
Double TRAP = bad.

Just so I'm clear... Does a short pipe that would hypothetically go between my drain-to-wall pipe and my trap which would lower my trap not exist or is it not legal for code?

ben's plumbing

not sure I understand you..but again.. if you open wall cut off pipe that is existing connect to vent instaLL TEE OR WYE to new height connect to existing lower drain line...hope you understand this... ps I dont know how to post a picture..HA HA that is sad...

mystic_cobra

I understand your description of how to lower the drain pipe that goes out the wall and I appreciate your assistance.

I'm asking if I can insert some piece of pipe between my metal trap and that 90 deg bend (where the white thread tape is in this picture below) that would lower the trap so I could make the connection without cutting into the wall?

As for posting pics on forums, I upload them to imageshack (free pic hosting) and then link to it from the forum post.

ben's plumbing

Ok think i understand..you could try it it is very close to flow line...so you want to lower the j bend to pick up disposal making the trap longer...never did it ...try it.. could work.... let me know...

mystic_cobra

Ok, cool. I think we're on the same page now.

So, J-trap, P-trap... all the same?

plummen

Can you post a better picture?

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