JaCkaL829
Member
Hello all,
I have a half bathroom, powder room (toilet, and lavatory) that are on their own seperate branch that tie into the main vertical stack in my basement. The drain for the toilet and lav are mostly old, 4" cast iron that are at the end of their life, cracks throughout the line. I'd like to cut remove and replace with pvc. Initally everything I read was 3" was perfectly suitable for this application, but now I'm wondering if I'll have clogging issues since the horizontal run hits a 45 elbow and travels about 2' into a wye which is in the main stack. I have read pros/cons to 3" vs 4". Someone mentioned 4" might not have enough flow if it's only on a branch that has a toilet and lav on it. I called my retired plumber and asked him about it, and he said it didn't matter. I also called and e-mailed my town's plumbing subcode inspector but he hasn't gotten back to me.
This job requires a lot of planning, and I'd really like to get it right the first time. The pros to a 3" drain line is I feel it would be easier to work with smaller fittings, and I'll have a lot more space to ensure I get the correct slope, and for the one horizontal turn that has a drop in it. I'm just unsure if reducing the size of the pre-existing pipe is a good idea. The 4" will cost more, and I perceive may be a little more difficult to work with, but I feel once it's in there should be no question of it working seeing how that's what is there right now and I have no clogging issues.
I know 3" is minimal and should easily handle my half bath, but I also read people saying you should never reduce a drain size, so something I though would be real cut and dry isn't.
Any help or advice would be appreciated!
I attached a picture: the top left corner is the end of the half bathroom run and where it transitions into a 45 elbow, with about 2 feet (drainout included) then goes into a wye in the main 4" stack.
I have a half bathroom, powder room (toilet, and lavatory) that are on their own seperate branch that tie into the main vertical stack in my basement. The drain for the toilet and lav are mostly old, 4" cast iron that are at the end of their life, cracks throughout the line. I'd like to cut remove and replace with pvc. Initally everything I read was 3" was perfectly suitable for this application, but now I'm wondering if I'll have clogging issues since the horizontal run hits a 45 elbow and travels about 2' into a wye which is in the main stack. I have read pros/cons to 3" vs 4". Someone mentioned 4" might not have enough flow if it's only on a branch that has a toilet and lav on it. I called my retired plumber and asked him about it, and he said it didn't matter. I also called and e-mailed my town's plumbing subcode inspector but he hasn't gotten back to me.
This job requires a lot of planning, and I'd really like to get it right the first time. The pros to a 3" drain line is I feel it would be easier to work with smaller fittings, and I'll have a lot more space to ensure I get the correct slope, and for the one horizontal turn that has a drop in it. I'm just unsure if reducing the size of the pre-existing pipe is a good idea. The 4" will cost more, and I perceive may be a little more difficult to work with, but I feel once it's in there should be no question of it working seeing how that's what is there right now and I have no clogging issues.
I know 3" is minimal and should easily handle my half bath, but I also read people saying you should never reduce a drain size, so something I though would be real cut and dry isn't.
Any help or advice would be appreciated!
I attached a picture: the top left corner is the end of the half bathroom run and where it transitions into a 45 elbow, with about 2 feet (drainout included) then goes into a wye in the main 4" stack.
