Ask Me Help Desk - Tap into the 4" drian pipe

I want to add a stationary tub downstairs in the laundry room. The 4" stack pipe that the upstairs toilet and sinks drain into is close by. So I was thinking that I could cut a section out of it just before in goes from PVC to cast iron. Use one of those rubber sections with clamps
And then reduce it down to a P trap for the tub. What do you think?

Hi Len...

I would recommend that you use a 4"x2" PVC wye (1st pic.) and a street 45 degree fitting (into the wye to bring 2" branch horizontal...2nd pic.) and install them into the 4" stack using 4" shielded clamps (see 3rd pic.) Then install a 2" Dandy cleanout (also called a test tee). Then install a 2"x1.5" reducing coupling (not shown)and an AAV (air admittance valve.. see 4th pic.) within 5 feet of the tub and then finally install the ptrap (aav with trap should look similar to last picture when combined). The AAV should be a minimum of 6 inches above the p-trap.

You need to install the AAV as a minimum or the tub ptrap will be siphoned evey time you flush toilet or drain a tub from upstairs and allow sewer gasses into the house. You could also run an individual vent in place of the AAV (this is best job) and run that over to other vents in the room (washing machine? ).

I would not recommend the rubber fernco fittings... ok? They are not only illegal for this purpose they have no strength and will collapse over time from the weight of the pipe/fittings from above.

Be careful when cutting into the stack and be sure that there is no excess weight on it before cutting into the stack (install a 2"x4" under pipe as turns to go horizontal to support weight of stack even if PVC... safety first).

You will also need a 1.5" desanco fitting (transitions from pvc pipe to tailpiece), 1.5" PVC pipe, PVC cement and primer, and a flanged tailpiece. You will also need any other fittings, like 45s, etc. that I can't determine for you...;) You can use the 4" pipe you cut out to install into the end of the 4"x2" wye fitting.

Let me know if need more info...

MARK

Quote:

Originally Posted by len69car

I want to add a stationary tub downstairs in the laundry room. The 4" stack pipe that the upstairs toilet and sinks drain into is close by. So I was thinking that I could cut a section out of it just before in goes from PVC to cast iron. Use one of those rubber sections with clamps
And then reduce it down to a P trap for the tub. What do you think?

I think you're going to be in big trouble if you use a rubber coupling on a stack vent. Use a shielded coupling instead,(see image) you will have much better support.

Quote:

I was thinking that I could cut a section out of it just before in goes from PVC to cast iron. Use one of those rubber sections with clamps
And then reduce it down to a P trap for the tub

Not going to be that siumple! You will have to vent the slop sink. This can be done in one of two ways.
I) you can run a vent up to the attic and revent back into a existing roof vent **or** 2) you can install a AAV,(Air Admittance Vent) just downstream from the trap, (see image). Your choice! Good luck, Tom Once again Mark and I are posting on top of each other. It's a good thing that we mostly agree

DEsanco fitting I could not post at last post... ;)

Dandy cleanout, too...

Hi TOM!

Thanks, you guys are great! I'm sending you some pictures. I notice that there is what looks like a clean out on the cast iorn. Is there a way to attach a drain there? You will also see a faucet on the other side of the wall is the downstairs shower. This is what they call a split foyer house. The down stairs is all finished. This spot in this corner is the only place I can put a tub. Hope this clears things up a bit. I sure appreciate all the good suggestions.

Hi Len...

Pictures always help!

Change the 4"x2" wye and street 45 I suggested to a 4"x2" sanitary TEE fitting.. see 1st picture. You want about 1/4" pitch per foot of drain line.

All else stays the same as posted at last post... ok? You cannot connect into the 4" cleanout... ;) Would be nice but very illegal and could be an issue if you went to sell the house as home inspectors look for this stuff like GOLD! MAkes them look good when they find stuff... you know.

I also think I see a 2" vent that runs behind/beside the 4" stack. You could take an individual vent from the laundry tub and connect into the 2" pipe or you can use the AAV we discussed earlier. Again, in your area, AAVs may be illegal so may be a good idea to connect into that 2" vent if you can...

Let us know what you think...

MARK