Help Replacing 1930s 4 Way Cast Iron DWV Pipe

[Europe72dead]

I’m trying to replace the below fitting in order to drain vent both a 2” run (sink, tub, shower) as well as a 3” run (toilet). The original stack was 4” cast iron and will be replaced with 3” PVC.

I’ve come up with two solutions but both have issues. The issue with one is that I’m using an illegal side inlet fitting that also has (2) long sweep 90 elbows. The issue with the other is that the vent (3” stack”) is below the line of flow for my 3” toilet pipe.

Would love to hear which method you would use. A drop ceiling isn’t an option. Maybe there’s something I’m not thinking of?

thanks!!!

 

[wwhitney]

What's going on upstream on the 2" line? Is the lav dry vented, and is it properly wet venting the tub and shower? If so, it could wet vent the WC as well, and you could come through the joist with the 2" line to a 3x3x2 combo to join the WC, and then a quarter turn 90 or san-tee to turn down, assuming that would fit before you hit the wall. The san-tee would be for maintaining the dry vent above if that is required for some reason.

As to your two configurations, the fitting in the first one isn't illegal if the side entry has the same curvature as a 2" san-tee would have. I believe that if your fitting doesn't, other fittings by the same or other manufacturers do. The double LT90 is unfortunate; you can't make it work with (2) 45s? Using a street 45 in the side inlet san-tee?

The second configuration looks OK, what's the issue with it? Since the 2" line coming in is presumably already vented, you could also swap the two horizontal connections to the stack: a (street) 3" san-tee on top for the WC, and a 3x3x2 wye below that to pick up the 2" drain.

Cheers, Wayne

 

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[Jeff H Young]

I like the last pic with the 2 inch line and a 45. the w/c could have had a 3 inch santee instead of a combi. it will fit in cieling better.
the 2 inch picking up a tub and lav should have vent at lav. I think this should comply and work fine

 

[Europe72dead]

Hey, thanks for the responses.

the 2” run connects a sink, shower and tub to the 3” stack. The sink and shower have their own dry vent and both wet vent to the stack. Before reaching the stack, the tub connects into the wet vent to the stack (only about 4-5’ away from stack).

First concept- the 2” side inlet does have curvature similar to a 2” sanitary tee. The 2 LT90 elbows are what I’m concerned about. No room to do it with 45s. I know you should avoid elbows in the horizontal position but will the long turns be fine?

Second concept- The combo 3” is above the vent which would cause it to poorly vent. Ideally I’d use a 3” sanitary tee here but I can’t because it would position the 3” pipe too low and I don’t want to put in a drop ceiling (the 2” inlet can’t be raised at all in order to maintain proper pitch downstream). Since the combo sticks out I was going to cover it with crown molding.

I’ve been told by a few other plumbers that the first concept is better but wanted some other ideas, thoughts.

 

[wwhitney]

the 2” run connects a sink, shower and tub to the 3” stack. The sink and shower have their own dry vent and both wet vent to the stack. Before reaching the stack, the tub connects into the wet vent to the stack (only about 4-5’ away from stack).

So none of those fixtures depend on the stack for venting, and you don't need to use a san-tee to connect to the stack. That makes the 3" WC san-tee over a wye for the 2" line a viable option.

First concept- the 2” side inlet does have curvature similar to a 2” sanitary tee. The 2 LT90 elbows are what I’m concerned about.

If you stick a street 45 into the san-tee with side inlet, can you rotate the fitting a full 45 degrees without hitting the joist? Then you'd need to rotate the closet bend 45 degrees and use another 45 to connect the WC drain up. Not sure if that is worth it.

Second concept- The combo 3” is above the vent which would cause it to poorly vent.

Not an issue, WC's don't have to follow the trap weir rule. They intentionally siphon and don't need to use a san-tee to connect to the stack, the combo is fine. You're still wet venting the WC with the lav/tub/shower coming in above the WC, but that's also generally allowed. [NJ uses the NSPC, which is a less common plumbing code that I'm not as familiar with.]

Again, have you considered, starting at the stack and going upstream: 3" san-tee, street 3x3x2 wye, with a (possibly street) 45 on the 2" branch inlet to pick up the lav/shower/tub, and the WC coming into the straight inlet on the 3x3x2 wye?

Cheers, Wayne

 

[Europe72dead]

I’m sorry I misspoke, the tub does actually use the main 3” stack for venting which is why I want to connect the 2” run to a san tee inlet.

will see if the pivoting and using 45s work in the morning.

thanks.

 

[wwhitney]

I misspoke, the tub does actually use the main 3” stack for venting which is why I want to connect the 2” run to a san tee inlet.

That's not actually possible if the single 2" drain carries the lav, shower, and tub. The tub trap needs to be vented before or as it joins any other drains. So if the tub is joining the lav and shower before they jointly hit the stack, then the lav/shower is wet venting the tub; the stack is not involved in venting the tub (regulations-wise; it may still help physics-wise).

Cheers, Wayne

 

[Jeff H Young]

looks good from here . dont see any tub shower or lav so if you got question still on those perhaps show that layout

 

[Europe72dead]

If you stick a street 45 into the san-tee with side inlet, can you rotate the fitting a full 45 degrees without hitting the joist? Then you'd need to rotate the closet bend 45 degrees and use another 45 to connect the WC drain up. Not sure if that is worth it.

A version of this seems to work perfectly!!! Anything look off to you or is this the best approach? The closest elbow will actually end up exactly where it’s located in the photo (it’s being relocated closer to the wall).

 

[wwhitney]

Looks good as long as the fact it's a few degrees off parallel to the joist doesn't cause you trouble on the other side.

BTW, the top plate should be reinforced as per:

https://up.codes/viewer/new_jersey/irc-2018/chapter/6/wall-construction#R602.6.1

Cheers, Wayne