Please help - Need advise on trap and venting

Hello - I have what appears to be an unvented bath trap. Pic shows the current set up and what I'd like to do about it. Depicted plumbing is in my cellar. The bath drains into a 4" horizontal pipe downstream from a vertical 4" stack that goes throught the roof (single storey bldg) via a 2X6 stud wall. The horizontal runs directly below the wall. The horizontal is properly sloped and is 17" below the floor at the vent. The plan is to install a 16" trap arm (2" pipe) via a tee into the vent stack. My understanding is that I will the have to replace the tee connection between the horizontal and vent stack with a wye. A 4" vertical toilet pipe currently drains into the horizontal pipe via a tee 14" upstream from the vent stack and I plan on changing its tee into a wye as well. Does my plan allow proper venting of the bath drain and toilet? Thank you.

What's your reason for doing all that? If you are doing as part of a renovation then yes, take the time to change it but if you are just doing it because you have an unvented trap I suggest letting sleeping dogs lie. Its been that way for awhile so unless it gets seldom use and the trap dries out, leave it be.

IF it is an exact representation of the tub drain, then it is an "S" trap and the new connection will correct it, as long as there is not an additional bathroom on the floor above it. From the way it was done, it appears to have been a DIY homeowner installation.

Thanks

TS and HJ: Thanks for your responses. TS: To answer your question, this is part of a renovation project. I'm replacing pipes upstream from what I've drawn in order to deal with some drain slope issues and thought I might put everything else in order. I was just unsure about proper venting of the bath drain and toilet.

No, your plan does not allow for proper venting of the toilet IF in fact you have another toilet that drains upstream on the 4 inch line you are currently connected to. You would have to connect the toilet to the vent stack in the same fashion as you are connecting the tub drain. AND the tub drain would need to connect the vent stack above the new connection point of the toilet, not below

Thanks, liquidplumber. There is no toilet upstream but there is a bathroom sink and a kitchen sink. Does the rule you mention apply to these?

If the bathroom or kitchen sink is vented, and both should be, it will vent the toilet. And once you have an independent vent for the tub you can connect it anywhere you wish to. It would only have to be "connected above the toilet connection" if it DID NOT have its own vent.

plethodon said:

Thanks, liquidplumber. There is no toilet upstream but there is a bathroom sink and a kitchen sink. Does the rule you mention apply to these?

Click to expand...

Nope, you only need to individually vent a fixture if its tying directly into a drain line downsteam of a toilet. In your example, there would be no need to vent your toilet first before tying in. (as there is no toilet upstream) The line itself will serve as the vent for the toilet.

HJ states **** And once you have an independent vent for the tub you can connect it anywhere you wish to. It would only have to be "connected above the toilet connection" if it DID NOT have its own vent.***** Which is exactly correct. In your diagram above the 4 inch vent stack would become the individual vent for the bathtub. In my earlier posts i was mentioning the upstream connection for the tub IN CASE you needed to tie the toilet into that 4 inch vent stack (to vent the toilet) before you tied it into the drain line. Make sense?

Thank you

Thanks to all of you for the help.