Any plumbers here?

Ultradog MN · Apr 13, 2023

I hope this doesn't rile up the hornets here like electrical questions sometimes do.
The black pipe in the photo I installed 14 years ago when I replumbed the whole house.
TWO 3in lines dump into the 3in vertical.
It was all inspected then and passed without issue.
We added on to the house 4 years ago and I framed in for a 3/4 bathroom.
Am finally getting around to finishing that bath.
Notice the 3in white pipe. It is just sitting there to show where I want to run the new drain.

This is my question:
Can I dump THREE 3in lines into that 3in vertical?
Not asking how to connect white pvc pipe to black abs pipe or how grandpa might do it.
I need to know what is code. I know that code varies but what is customary or rule of thumb.
Thanks

cjunrau · Apr 13, 2023

Yes you can. At least in Manitoba. Doesnt matter how many baths just one 3 inch goes out

kcm.MN · Apr 13, 2023

Only people that live in your area are likely to know what your local building code states, but I would assume it would be OK. Your 3/4 bath has no bath; just sink and toilet. Even with everything in ALL directions draining at the same time, adding a 3/4 bath certainly is not going to over-tax the 3in vertical line.

If you want to be safe, call and ask your building codes office. Of course since you're asking here, I assume you don't want to call them. 8)

paul · Apr 13, 2023

Im just a simple dirt farmer so I dont know, but I believe it has more to do with how many and what type of fixtures will be flowing through that vertical pipe, and not really about how many 3 inch pipes you attach to it.

You need to count sinks showers toilets and see how many are flowing through the vertical pipe. Im pretty sure you will be in good shape.

They get more fussy about the vent situation, when you add on you can easily mess up the original paths/ requirements of the vents. And you didnt ask about that and it becomes more of a debate so just forget I said anything.

Paul

Ultradog MN · Apr 13, 2023

Maybe should have added this before...
There is a full bath - toilet, sink tub/shower on the second floor.
Right now on the 1st floor are the kitchen and a half bath.
We are adding a 3/4 bath - shower only + toilet/sink AND hookups for a stackable washer/dryer.

Janicholson · Apr 13, 2023

If the 3 inch Down pipe enters a 4 inch floor adapter, I would plumb the Y at bottom of the existing two 3 inch black, into a 4 inch pipe to the floor. I would sweep T the new white 4 inch into this. Jim

ss55 · Apr 13, 2023

If you are afraid to contact your local building inspector, now-a-days you should be able to look up your local building codes and read them on line anonymously. Keep in mind that anything we say here, what the local church group tells you or what they say at the tavern will not change your code requirements, LOL. Codes are meant to protect future home buyers (and their insurance companies) from the shortcuts and mistakes of builders and previous owners.

As others have mentioned, proper venting is what prevents the flow from one bathroom from backing up and back flowing out another drain or into the kitchen sink. Venting is not always easy to understand.

Ultradog MN · Apr 13, 2023

Jim,
Yes.
That is my back up plan.
When I replumbed the house I opened the floor and moved the main stack close to the wall.
It wouldn't be the end of the world to reopen the floor replace the 4in clean-out and run a 4in riser a few feet up. Then wye the white pipe into that.
But would avoid that if I can.

Ultradog MN · Apr 13, 2023

I did have the foresight - 4 years ago - to run the 2in vent from this new bathroom up through the framing into the attic so I know that part is good.
If I had the foresight - 14 years ago - to know I would get married and she would want a bigger house I would have put a 4in riser in the basement

Scott 730 · Apr 13, 2023

Before pulling part of the floor out, I would first try to remove the 4" to 3" bushing from the top of the cleanout T. I have peeled fittings out before with VERY sharp wood chisels. A sharp 1/4" chisel works well to slowly peel out small pieces at a time.

Stan Coryell · Apr 13, 2023

Not sure what code you are uses..
Sewer is sized by DFUs.
According to the ICC, your 3 stack should be good for 48 DFUs. Your bath and clothes washer should be 7 DFUs (if I read it right). You will have to add the other two lines up. If you have to, they make a drill bit to cut the pipe (bushing) out of the hub. Google Hub Saver

ICC

Vito · Apr 13, 2023

Do they allow studder or popper vents in your state?

Vito

Janicholson · Apr 13, 2023

If allowed in code, I see no issue with your Plan A. Jim

john in la · Apr 13, 2023

Im my state a 3 inch vertical pipe can handle two 3 inch horizontal pipes. Once you go above 2 you need to add all the fixture units to make sure you are not exceeding the vertical pipe capacity. Once the pipe turns and goes back horizontal it needs to be 4 inch.

Frankmn · Apr 13, 2023

Always thought the rule was T's in the stack, Y's on their back.Drop it into a T down by floor

sandcastle1 · Apr 13, 2023

here in Ohio a 3/4 is a shower, sink and toilet.

Stephen Newell · Apr 13, 2023

3 is a little small for a main drain. You might overload the system with another line

Stan Coryell · Apr 13, 2023

Maybe he should put a 16 in? Did you do any math?

Ultradog MN · Apr 14, 2023

For now I am going to continue plumbing everything right up to that white elbow in the photo and keep the job moving forward.
Am thinking I will upsize that 3in riser to 4in tho. Just to be on the safe side.
I searched for that tool you posted yesterday but not long enough to sift through all the ads and find it. That would make it easy. Do you have a link?
Thanks to all of you guys!

gary49 · Apr 14, 2023

Code allows up to 3 water closets on a 3 stack for residential plumbing. Just cut in the new 3 line into your existing stack.

Any plumbers here?

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