Good morning Glenn, If you're going to discharge into the washer stand pipe you will not need a trap. You can not double trap a fixture. Just come off the drain with a DWV elbo. We slope our lines 1/8" to the foot. That will give you 1 3/8" fall for a 11 foot run. You MUST give a drain line slope for proper drainage. I know of no shower bases with a side outlet drain. Use DWV elbos or short sweeps and a few turns in the drain line shouldn't be a problem, your snake will have no problem going in through the shower drain. Connect to the washer stand pipe with a 2" drainage tee or a combination wye and 1/8 bend. There should be no problem taking a shower and doing laundry unless the washer line clogs and backs up. Then it will back up at the lowest point, the shower base. More questions? I'm as close as a click. Tom

Tom,

I'm in the process of installing the shower. Turns out the drain I have access to a 1-1/2" PVC pipe, not a 2" as I thought.

First question, will a 1-1/2" drain be enough for a shower? It will be shared with a kitchen sink and maybe another sink.

Secondly, I also want to better understand the idea of a running P-trap. Instead of a traditional P-trap, I want to do the following (which I think is a running P).

I will come out of the drain fixture under the shower and put a 90 degree 1-1/2" elbow as soon as possible pointing horizontal. I will run a piece of 1-1/2" PVC pipe along the floor (maintaining a 1/8" per 1 foot drop) out past the edge of the shower (about 3 feet), then turn up with an elbow, and then horizontal with another elbow. From here, I joint the 1-1/2" drain pipe.

Water will remain in the 3 foot pipe, which forms the gas seal. This should save me having to raise up the shower basin by an additional 3 inches (the difference between the running P and the traditional P.

I'm worried about water standing in the shower. To avoid this, I'd need to make sure the point where the water falls into the drain needs to be a bit below the floor of the shower (ie the water level will be a the point where the water can get into the final drain.

Thanks for your help.

Hi Glenn, If you plan on holding to code and calling a inspection then I have some bad news for you. A running trap is nothing more then a unvented "S" trap laid on its side. "S" traps are outlawed in all state, county and local codes. If you were going to discharge into the washer stand pipe, upstream from the washer trap, you would'nt need a trap.l However you're planing on to discharge into the washer drain which is downstream. You will need a "P" trap installed. More bad news. You may only run 5', (using a 2"drain line) from the shower trap to a vent, you are planning on 11'. Showers call for a 2" trap. Still more bad news. The limit of fixture units you may put on a 2" line is 3. A shower stall takes 2, a kitchen sink takes 2, a lavatory takes 2. Can you see the problem here? (1) A shower loads up with grease and hair a 1 1/2" drain with no pitch will clog up in no time. (2) 2 elbows in the drain line will make it clog up that much faster. (3) A washer pump discharges with much force and pressure. If the shower is down stream from the washer I can guarantee you that it will back up in the shower stall if there is even a tiny blockage . My advice, Take up the floor and run the job in 2" for the shower and lavatory. For the kitchen sink increase to a 3" drain, (especially if you have a garbage disposal unit. Bottom line! If you undersize your drainage system and then overload it you're asking for trouble. I'm sorry for being so negative but better you face it noiw instead of after the job's done. Good luck, Tom PS. You should check my answers with your local plumbing inspector to double check.

Tom,

I'm glad I checked back with you. And thanks for "being negative", I want the bad news now, not after the project is finished. I've mixed projects, so let me clarify and see if that helps my situation.

The washer is on a separate drain pipe, so it is not a factor for the shower. The distance from the shower to the 1-1/2" drain pipe will be less than 5 feet, with probably only a single 45 degree elbow in it. The drain pipe has a vent on top of it. So that means that the vent is within the recommended 5 feet, as well as a shorter distance for the drain.

If I am eventually ending up in a 1-1/2" drain pipe, does it matter if the shower drains through a 1-1/2" pipe or a 2" pipe? Isn't the limiting factor the 1-1/2" drain pipe? Or does the 2" line help move grease and hair along better. In either case, would a more aggressive slope, maybe 1/4" instead of 1/8" per foot prevent clogs, especially if I went with a 1-1/2" shower drain?

Thanks,

Glenn

I see you're on line so I'll answer right away. The minium size for a shower trap and drain line is 2". 1 1/2" is not acceptable. Keep your slope between 1/8 and 1/4". To little slope and you won't have drainage. Too much slope and the liquid will drain away so fast it will leave the solids behind. You said, " The distance from the shower to the 1-1/2" drain pipe will be less than 5 feet, with probably only a single 45 degree elbow in it. The drain pipe has a vent on top of it. So that means that the vent is within the recommended 5 feet, as well as a shorter distance for the drain." What drain line are you talking about, the washer and is it a horizontal or vertical drain pipe? In any event you can't discharge a shower into anything less then a 2" trap and drain.

FYI, I completed this project, and it worked fine.

I ran 2" PVC pipe inside the newly built wall. It went from 7-1/2" above the floor in the laundry room, above a door, down the wall and into a 3" drain pipe. I left the end of the 2" pipe sticking out from the walll.

I then took two washer discharge hoses, and spliced them together with two pipe clamps and a coupling. (I obviously could have used a longer hose if I could have found one, although the discharge hose had the advantage of having a bend it at the end) One end went on the washer discharge, the other end went into the 2" pipe at the top of the wall. I found a nifty rubber cap with a hole in it that held the hose into the pipe.

I did not put a check valve in the hose, but there does not seem to be much backwash from the longer hose.

Thanks again for the advice. My handiman was skeptical while he was building the walls, but was a believer after he saw it working. He's going to incorporate it in his future jobs rather than cut into the slab.

Hey Glen,
Glad things worked out Congratulations on competing your project. I'm glad if I helped a little. If we can ever help again just call out. Regards, Tom