Installing new cabinet -- need to move kitchen drain line

[Cbrillow]

Hello,

New to the forum. Have been doing a lot of reading to try to find a similar situation and to acquaint myself with terminology, but I may still make rookie mistakes and ask for your indulgence.

We're finally able to spring for replacement cabinets in our 1970-built home, and I'm doing the install in order to make it affordable. The problem is, the drain line from the kitchen sink runs horizontally (well, almost...) through the cabinet to the left of the base. This was an inconvenience with the existing cabinet, which had two drawers at the top and a single 11" shelf about 12" up from the bottom. The drain ran right down the center of the shelf, making about 40% of it unusable. At the left side of the cab, it makes a turn and angles towards the front, where it disappears into the wall, where it connects with the stack and, presumably, the vent.

The replacement cabinet that we've purchased has the similar drawers at the top, but it also has two full-width drawers located about 1" and 12" from the cabinet bottom. These drawers are extend almost all the way to the back, so it's clear that I can't put this cabinet in place with the drain line situated as it is.

This photo shows the basic configuration as it currently exists:

Here are a couple of views showing a bit more detail:

I would like to move the drain line by rotating the P-trap 90 degrees and taking the line through the back wall of the cabinet before turning to make the horizontal run. This would get the line out of the cabinet space, except where it must turn in towards the front along the left side wall. This would effectively move it back about 8", where it would be concealed behind a 'false' back added to the back of the cabinets. (it would be accessible, if needed for repairs...) Is this an acceptable practice?

Also, I would prefer to accomplish this with PVC pipe, rather than copper. Is there some kind of adapter/fitting that connects 1-1/2" PVC to 1-1/2" copper at some point near the termination at the stack?

I would really appreciate knowledgeable comments on these two questions, as well as suggestions on other issues that are advisable or mandatory in updating the disposal, dishwasher and supply lines in the sink base.

Thanks for bearing with me on this rather long post!

 

[Cookie]

Yes, there is a banded coupling made that is specifically for the purpose of transitioning from copper to PVC. What is the distance going to be from the T to the trap?

 

[Sponsor]

 

[Jadnashua]

You need to vent the sink before you go horizontal with it. If you can't use an atmospheric vent that goes up through the roof, you might be able to use an AAV, if allowed where you live. Otherwise, the trap is likley to get sucked dry and allow sewer gases to come through. That one rubber coupling is not designed for use above ground...you should be using a banded one like there are on those in the wall.

 

[Cbrillow]

Yes, there is a banded coupling made that is specifically for the purpose of transitioning from copper to PVC. What is the distance going to be from the T to the trap?

Thanks for your response. I'm not sure what you're referring to as the "T", but the distance from the trap to where the pipe enters the stack is currently about 5 feet.

Running through the back wall and along the outside of the cabinet would add no more than 2 feet. I've read some comments that it must be less than 8 feet from trap to drain -- is this what you're asking about?

 

[Cbrillow]

You need to vent the sink before you go horizontal with it. If you can't use an atmospheric vent that goes up through the roof, you might be able to use an AAV, if allowed where you live. Otherwise, the trap is likley to get sucked dry and allow sewer gases to come through.

Hi Jim, Thank you for responding.

My presumption is that the venting is done inside the wall, as the drain line is "Y"ed with another 1-1/2" pipe that runs vertically up inside the wall. I've seen some diagrams online that show something like this as a part of a more comprehensive loop. I know that this other pipe is not a drain, because I ran water from upstairs and from the bathroom on the other side of the wall from the cabinet. I was able to verify that the upstairs water was coming down the stack, and that the bathroom water was going through a separate 1-1/2" copper line into the stack below the floor. So it seems logical that the pipe inside the wall is part of a vent.

That one rubber coupling is not designed for use above ground...you should be using a banded one like there are on those in the wall.

Thanks -- not surprised about this. I had to cut the line several years ago to clear an unusually stubborn clog, and put the coupler in so that I could do it again in the future. (I once called in a licensed plumber to clear this line, and he couldn't do it...)

 

[Cacher_Chick]

What everyone is trying to tell you is that the developed length of the pipe is too long between the wier of the trap and the vent. Also, because of the use of the bends in in wall, you have an S-trap, which is not allowed.

You have to meet the code for the location of the home. Here where I live, that pipe could be a maximum of 5 feet long IF it were dumping straight into a sani-tee, which yours is not.

I would start by looking at the possibility of installing a vertical drain & vent stack behind the sink that could connect to a drain in the basement or crawl, and a vent in the attic.

 

[Cookie]

Yes, that is what I was asking, and you answered your own question about the distance of the pipe.

The drainline leaving the trap must go to the T fitting. A "T" is a "T".