Hi all – thanks in advance for a site that has already been incredibly helpful.

I am in the middle of gutting and remodeling our bathroom and would like to replace the cast iron waste pipes with PVC.
About the house: Duplex, over/under. Each unit is a one bedroom with a single full bath in each unit. City sewer. Previous owner replaced the cast iron from the basement floor up to somewhere in the middle of the first floor with 4”PVC. Above that is 4” cast up through the roof. Have not had any problems with the waste service since we bought the house 5 years ago. We plan to own the house for a long time, and I don’t ever want to rip up the bathroom floor, so I figured I might as well replace the aging cast with PVC…plus it lets me get it up to code. I’m a diy’er with limited experience, and so I apologize for not having the technical terms for certain things.

I’m struggling with the layout of the new system. In the attached photo you will see the closet 90 for the toilet with two 1.5” inlets. The inlet on the left (brass) is for the bathroom sink, inlet on the right (black ABS) is for the bathtub. From the center of the hole for the toilet back to the edge of the vertical 4” cast is 14.5”. Directly above the tee that this flows into is another tee where the kitchen sink empties into it. The kitchen sink is located 5’ up the same wall the bathtub is on. The sink used to be located just on the other side of the cast and was relocated at some point. They ran the drain pipe through the back of the cabinets --- I’d like to use this opportunity to clean it up.

Current:

[www.dropbox.com]

Here's my proposed setup:
Replace the stack with 4” PVC. Add a 4x4x3 tee. Add 3x3x3 wye to the tee --- one end of the wye goes to a closet 90 for the toilet, the other end reduces to 2” and goes to another wye where the tub and a new drain line for the kitchen sink tie into it - all of that in 2". I would then drain the bathroom sink into a 4x4x2 wye that I would put on the vertical stack.

Vents shown in red. I would connect the vent and go up in the wall next to the tub feed lines, then horizontal and into the stack at about 50" high. I could do the same for the sink drain. Should I add the vent to the 2" bathtub and kitchen sink horizontal (sloped) drain with a tee or a wye? Vent should be 2" for tub/toilet/kitchen sink, correct?

[www.dropbox.com]

if you want to be up to code, you can not do what you propose.
i would use a 4 x 4 x 4 x 2 right hand inlet sanitary tee for the toilet and tub.
then use a 4 x 4 x 2 x 2 double sanitary tee for the lav and the kitchen. all of this is stack vented...
install a cleanout under the vanity and under the kitchen sink.

Thanks for your reply; that seems like a really easy solution.

The kitchen sink is about 6-7 feet away from the stack...but that's pretty close to the 5' maximum for 2" pipe. It already has an aav after the trap, so I could probably leave that on for good measure.



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Packy,

This is on the second floor, and all of the fixtures on the floor below (kitchen and one full bath) empty into the same stack as you propose. Am I still okay to do the same thing above them, or do I need to worry about venting all those fixtures as well. I guess this is the way it's always been...

piping the way i suggested will get you to code for a top floor bath and kitchen.
what goes on below will not affect the top floor but the top floor will affect the floor below.

Thanks, Packy. I really appreciate your help. There are no problems currently with the plumbing for the downstairs, and so I guess this shouldn't create new problems. I'll deal with bringing that up to code if I ever need to make changes or modify it.



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