Can I run new 1.5" line into 3" clean-out location?

[Jefrf]

My kitchen sink tends to back up because the line runs into original pipe (built in 1942) below the concrete basement floor. I snake it occasionally but it still gets slow. Who knows how much gunk has built up over 80 years or what the integrity of the metal pipe even is at this point! This causes it to back up into a small bar sink in my basement which shares that line. I decided it might be worth running about 20 feet of new 1.5" PVC from just below the kitchen, along the basement ceiling joists, over to where all of the other plumbing runs from three bathrooms, and close to the main stack. This is all nicely hidden in my basement laundry room. Just about where I would want to pop the new pipe into that room is a 3" line coming down from the second floor bathroom, transitioning to horizontal along the basement ceiling with a nice long sweep combo wye and 1/8-bend, and a clean-out threaded behind the sweep. (Shown in photo) The new kitchen line would be right in line with that clean-out, but I don't know if I can just run a 1.5" line straight into that. I suppose I'd have to provide another clean-out if I did. I'd also need to find the right fittings to go from female threads of the 3" clean-out to my 1.5" PVC.

Another option would be to leave the clean-out where it is, and running my kitchen line a little past the sweep location, maybe a couple of feet, and use a wye fitting to tie the 1.5" into the 3" along the horizontal run. The reason I'd rather not do this is because I don't think I'll have room to move the 3" line apart in order to fit and glue in a new wye fitting. Whereas working only on the open end where the clean out is would provide opportunity to start my glue joints.

I appreciate any advice here.

 

[Sylvan]

I never ran any waste line especially a kitchen less then 2" diameter

Knowing lines need to be serviced a 2" line with long radius fittings allow for easy water jetting to scour the lines to restore full flow

The difference in price from 11/2 -2" makes no sense not to use a larger diameter

 

[Sponsor]

 

[MACPLUMB]

2" Is what is required by CODE, I would use a 3"X 2" metal bushing, with a 2" X 6" galv. steel nipple with a no hub band coupling with a metal
covering to transition to your 2" PVC. pipe, run it all the way up to behind the kitchen sink with 2" X 11/2" X 11/2" San tee

 

[Jefrf]

I never ran any waste line especially a kitchen less then 2" diameter

Knowing lines need to be serviced a 2" line with long radius fittings allow for easy water jetting to scour the lines to restore full flow

The difference in price from 11/2 -2" makes no sense not to use a larger diameter

Sylvan, I left out some of the other detail that I didn't think mattered. I had professional plumbers run the drain for this kitchen in 2004, which was in a new addition over a crawl space. They ran 11/2" from the new sink over to where the old kitchen sink drained into the basement floor line, which was 11/2 or maybe as low as 11/4" from 1942 standards. It passed inspection, so I guess back then you didn't need 2" from the kitchen. Even though I would be grandfathered, I suppose I could get back into the crawl space and just run all new 2" up into the sink base cabinet since I'm going to run some new anyway, and bring it up to current code.

Whether its 2" or 11/2", my main question is still whether I can just tap into that 3" clean-out. Masterplumb77 seems to suggest I can, and that sounds like what I would have done. Would the no-hub (full metal band-I know not to use the two small bands) be an adequate location as a clean-out for that 3" line should the need arise ??

 

[Jefrf]

2" Is what is required by CODE, I would use a 3"X 2" metal bushing, with a 2" X 6" galv. steel nipple with a no hub band coupling with a metal
covering to transition to your 2" PVC. pipe, run it all the way up to behind the kitchen sink with 2" X 11/2" X 11/2" San tee

Thanks MASTERPLUMB777. One thing that concerns me is your suggestion of a metal bushing to transition down from 3" to 2". Since the plastic will be female threads, I'll need to put a stronger metal male thread into weaker female plastic. I've heard often that this can lead to breaking or leaking before the threads are tight enough. Is there not an appropriate PVC bushing which I could use for this to avoid risk of cracking?

 

[Reach4]

Is there not an appropriate PVC bushing which I could use for this to avoid risk of cracking?

Before ordering anything, measure the OD on the thread of that cleanout plug to make sure you have the thread size you think you do.

 

[MACPLUMB]

You will have a problem trying to tighten a Male PVC Adapter so it does not leak

 

[Sylvan]

Sylvan, I left out some of the other detail that I didn't think mattered. I had professional plumbers run the drain for this kitchen in 2004, which was in a new addition over a crawl space. They ran 11/2" from the new sink over to where the old kitchen sink drained into the basement floor line, which was 11/2 or maybe as low as 11/4" from 1942 standards. It passed inspection, so I guess back then you didn't need 2" from the kitchen. Even though I would be grandfathered, I suppose I could get back into the crawl space and just run all new 2" up into the sink base cabinet since I'm going to run some new anyway, and bring it up to current code.

Whether its 2" or 11/2", my main question is still whether I can just tap into that 3" clean-out. Masterplumb77 seems to suggest I can, and that sounds like what I would have done. Would the no-hub (full metal band-I know not to use the two small bands) be an adequate location as a clean-out for that 3" line should the need arise ??

Even the NYC 1939 plumbing code required 2" for a kitchen waste line

The plumbing codes give minimum requirements,,

The installing plumber should have used common decency and spent the extra $2.00 - $3.00 for increasing the diameter of the pipe .