ABS to PVC Repipe - assistance requested

[ProfessionalAmateur]

This forum has been super helpful the past few years and I'm now diving into a what I consider a much larger project.

I have a bathroom gutted and almost all of the ABS pipe for the house is exposed, dated 1967/68. I am putting the pieces of the puzzle together to tackle a re-pipe from ABS to PVC. The copper hot/cold lines will also be replaced. My hope was this would be a 1-for-1 replacement but the more research into plumbing codes and forums the more thats not likely.

Everything will be permitted, fwiw.

Open to recommendations or suggestions as you see fit.

To start, it is my understanding is the side inlet on a 90elbow can only be used for venting, please confirm.

• The shower and sink pipes are 1.5in and tie into a toilet 90/elbow with a side inlet. My understanding is that this inlet can only be used for venting.
  • The sanitary tee is either not allowed, or backwards, possibly both.
  • Note - The 3in toilet elbow is within 3ft or so of the main vent stack.
  • Note - the sink has venting, but the bath does not (see below).

Questions

1. Currently the bathtub has a direct outlet waste (ptrap) and overflow - Does the bathtub need to vent similar to the sink, or does the 3in toilet drain close to the vent stack provide proper venting?
   • Note - the ptrap for the bathtub is ~9ft of piping to the entrance at the toilet/90 elbow with side inlet.
2. Does the toilet need a separate vent or does the main stack vent count as its only ~3ft to the main vent stack?
   • I believe its fine the way it is, otherwise i could tie it into the vent stacking for the sink, if that's allowable.
3. Does the slope of the stack venting on second floor look correct?
4. Does the double wye with 1/8 on each side look kosher?
   Its tight up against the hvac and i plan to run a 22 at the top and remove the fernco.

 

[ProfessionalAmateur]

#3 has been answered and the slope is wrong as the water would pool in the corner 90, not to mention it needs to go higher before going horizontal to meet flood rim level rules. I plan to just run it straight up to the roof and tie it into the main stack horizontally there.

for #4 the existing looks to be a double wye with 22 1/2 not 45. I’ll update questions with new diagram.

 

[Sponsor]

 

[ProfessionalAmateur]

I will remove the toilet 90/elbow with a side inlet and tie the shower and sink drains into the 3 in with y combos.

Do the bath and shower require venting?

Is the double wye correct or should I use a double wye with 1/8, or double combo?

 

[wwhitney]

Your photos, diagram and text are a little bit hard to follow. But I gather you have side by side bathrooms, with a stack in between. Each bathroom has a lav, a tub, and a WC, with the drains connected in that order and then to the common stack. So my comments:

- In each bathroom, the lav needs a 1-1/2" dry vent taken off at the elevation of the lav trap (within 1-1/2" of fall from the trap outlet).

- With that, the lav drain can wet vent both the tub and the WC. A drain carrying only 1 lav, nothing else, can be 1-1/2" and still be a wet vent (under the IPC, in use in VA). The path of the lav drain between its dry vent takeoff and where it joins the next fixture to be wet vented (the tub) is not regulated any differently due to being a wet vent.

- The tub trap arm extends from the trap outlet to the wye where it joins the lav drain. For a 1-1/2" tub trap, that trap arm is limited to 1-1/2" of fall, which implies a 6' length limit if you have perfect 1/4" per foot fall (a shorter length limit if the fall rate is higher). For a 2" tub trap, the fall limit is 2", implying a 8' length limit at maximum fall.

- To wet vent the WC with the combined tub/lav, the drain needs to be 2". So the wye where the lav joins the tub needs to have a 2" outlet.

- A quarter bend with side inlet is not a sanitary pattern and may not be used to join the lav/tub to the WC. Instead use a 3x3x2 wye.

- The run of the WC drain between the closet flange and the 3x3x2 wye is not regulated.

- Joining both 3" branch drains to the stack with a double wye is fine. Note that the portion of the stack between the double wye and where the 1.5" lav dry vents rejoin the stack is optional; it is playing no role in venting anything.

Cheers, Wayne

 

[ProfessionalAmateur]

Apologies for lack of clarity and thank you for the responses.

I will use 2” all around for the lav and tub. Is a 3x3x2 wye recommended or would a long sweep combo be “better”?

Curious on this statement if I understand it correctly - do you mean the lav venting that ties into the double sanitee on the vent stack? If so, how/why does it play no role in venting?

”Note that the portion of the stack between the double wye and where the 1.5" lav dry vents rejoin the stack is optional; it is playing no role in venting anything.”

 

[wwhitney]

Is a 3x3x2 wye recommended or would a long sweep combo be “better”?

A combo is equivalent to a wye plus a street 45. Either works.

Curious on this statement if I understand it correctly - do you mean the lav venting that ties into the double sanitee on the vent stack? If so, how/why does it play no role in venting?

So your lav vents tie back into the stack with a double san-tee (conventionally "upside down" for venting)? I was saying the stack between the double wye and the double san-tee plays no role in venting and could be eliminated (but is also fine to leave). The vent path for each fixture is via the dry vent takeoff on the lav.

Cheers, Wayne