Installing a new 2" shower drain with 2" trap. This will tie into an existing 3" waste line 45 inches away, located in the same 16" floor joist space on the 2nd floor. I will tie into the waste line with MJ clamps (hope I have that term correct).

I had heard that with a drain line of 2", I may not need a separate vent stack to tie into. By the way, the 3" waste line already has a vent stack located about 12" off it.

Is a separate vent line required for my shower, or will the 2" drain line suffice?

If yes, I CAN tie into that existing 1 1/2" vent stack i mentioned above, but it will mean that my shower drain vent is about 5'6" from the shower drain and trap itself. I'm just not seeing the purpose of running a separate vent line from the shower, if the waste line i connect to already has a vent that may serve the purpose.

Any help greatly appreciated.

Any pictures available of the piping layout. If you can use the 3" as a vent depends on what is upstream of the tie-in point.

It is doubtful that the 3" pipe is a dry vent. If there is a toilet draining into that 3" pipe, then yes you will need to vent the trap. 1 1/2" will be fine.

Distances CAN BE relevant, but you cannot always connect to a pipe without a separate vent. It depends on what kind of pipe you are connecting to.

Thanks for the quick reply. Yes, the 3" line I am tying into is indeed a toilet waste line. It also picks up a 2nd floor washing machine drain that is p-trapped before hitting the 3" line.

It is the vent that is connected to that washer trap that i could tie into if need be.

I was @ Depot tonite and met a plumber there who suggested an inline vent from Oatey would work and that i do not need to run a separate vent line.

Is he right?



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Yes, it will work, provided that it remains accessible, is at least 4" above the trap, remains vertical, and that the vent pipe downstream of the shower trap rises vertically off of the drain pipe.

[i1337.photobucket.com]

I wasn't sure if I was working this site correctly. I didn't see my post i made last night until i went into edit mode...so I don't know if you got my post or not. there's a picture in my reply from last night - hope you can see it.

You wanted a pic...so here's one.

The pic shows the open ceiling space directly below the upstairs bathroom where the our shower will be installed. The right to left 3" ABS pipe crosses 2 floor joist spaces and is where i plan on tying into for the 2" shower drain. I will be connecting to the 3" pipe in that joist space on the right...from about 45 inches away. I will be placing a trap directly under the shower pan. The Wye joint i will install will be identical to the one you see if the left joist space...but located in the right joist space and coming from the direction i was standing when i took the pic.

So...the plumber i met @ Depot advised me NOT to use MJ clamps and go with the hard ABS pipe instead (Wye piece). My concern is that there is NO wiggle room to get a hard pipe wedged in there. How is this normally done if not with a flexible MJ?

I can get install an inline vent just above the floor in the bathroom just above where you see the connections in the left joist space. There will be a shower bench seat that will be available to place the vent into, and I will have an access panel to that to service the inline vent after a few years of use.

I can also install a dry vent that will tap into the existing venting system running to the roof. To do this, i have 2 options:
- if you see the pic, i have a vent line that is kinda hidden in the pic behind a copper line, that vents that 3 way trap you see in the rear (a washer drain line, a floor drain, and a spigot drain from our steam shower unit. These all tie in to a single trap that will always remain wet. I COULD tie into that vent line but i won't get much rise out of the line from where i have to come from (60 inches away). I'm not sure i will have 1.5 inches of drop (1/4 per foot).
- i can instead, go up thru the floor and tie into that same vent line, but higher up.
What is my best option (if the inline vent is acceptable, i would rather go that route).
Again...many thanks for your help.
Geoff



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