Hi folks:

I would like to install a shower that drains into the same drain as my washing machine.

Right now the washing machine drain, 1-1/2" ABS, comes in horizontally about 12" above the concrete floor into a 1-1/2" Tee on a vertical pipe. From this Tee, the vent goes straight up to the roof, and the drain, of course, goes straight down. Before entering the concrete slab it goes to 2" ABS and has a cleanout that is flush with the slab.

This vertical pipe (would this be called a "stack"?) is in a wall in the corner where I will be installing the shower, so it's pretty handy.

There is a cleanout directly above the cement slab.

Although I would only need to dig up a few square feet of concrete, I'm not all that crazy about the idea, having spent a couple of hours today doing that for the toilet--it wasn't fun. So, I'm thinking about platforming the shower.

So here is my intended setup, I'm wondering if anyone could comment on whether it would work:

1. I'm thinking of commissioning the existing cleanout as a junction to feed the shower drain into, i.e. finding an ABS fitting that goes male 1-1/2 to a threaded fitting into the cleanout. I'm interested in this simply because changing the current cleanout to a T would require digging up a fair bit of concrete (as it's flush with the slab).

2. I'd place a new cleanout just above the existing re-commissioned cleanout, between the washing machine Tee and the old cleanout.

3. I would put a P-trap between the shower drain and the re-commisioned cleanout/junction. I'm assuming that the min. height for the platform would be enough to put a P-trap in? And is a P-trap just a U-shaped fitting? What is the difference between this and an S-trap? I've read elsewhere that an S-trap is required.. I really don't know anything about this trap stuff so please be specific.

4. Question about dry/wet venting: would the section of pipe between the washer's Tee into the vertical pipe and the shower's "Tee"/re-commissioned clean-out be considered a "wet vent" since the venting for the shower would be shared with the drain for the washer? And if so, should I change this to 2" instead of 1-1/2"? (I didn't indicate this in my drawing below).

Here is a diagram of my proposal:
http://sawback.com/plumbing.jpg
Click here if it doesn't show up for some reason. (http://sawback.com/plumbing.jpg)


Thanks for the great site and to all of the experts who put so much effort into steering us neophytes right,

Tom Wolfe

Hey Tom,

Your layout would work only if the shower trap and drain line were 2" and not over 5 feet from trap to vent. Anything more then 5 feet and a vent will be necessary. As for a trap you are describing a "running trap" check local codes to see if this is allowed. I'm putting up images of the traps so you will know the difference. Regards, Tom

Hi speedball-Tom: Thanks for the quick response, so I can carry on with it this weekend!

I have another question that I added to my Question before I noticed your reply:

4. Question about dry/wet venting: would the section of pipe between the washer's Tee into the vertical pipe and the shower's "Tee"/re-commissioned clean-out be considered a "wet vent" since the venting for the shower would be shared with the drain for the washer? And if so, should I change this to 2" instead of 1-1/2"? (I didn't indicate this in my drawing below).

... and a couple of questions about a "running trap". Is this different from P or S traps because it is installed in a horizantal stretch of drain? I.e. do P and S traps require a vertical feed? And if so, how would you satisfy code requirements for a basement shower like I'm trying to build?

... regarding running traps, is there any "vertical feed" requirement to make them work? E.g. should there be a drop of X inches for a 2" pipe before entering the trap?

... will the washer drainage siphon out my shower's " pipe before entering the trap?

.... will the washer drainage siphon out my shower's " in the setup I've described? Why is a " in the setup I've described? Why is a " illegal in some places and not other?

To answer the question of the distance between the vertical drain pipe and the shower drain: it will be about 18", and in this space, above the slab, I would be installing the running trap. As you indicated I should use 2" pipe/trap/etc.

Thanks again speedball-Tom, you do an excellent job on this forum.

Regards,
neophyte-Tom

"Question about dry/wet venting: would the section of pipe between the washer's Tee into the vertical pipe and the shower's "Tee"/re-commissioned clean-out be considered a "wet vent" since the venting for the shower would be shared with the drain for the washer? And if so, should I change this to 2" instead of 1-1/2"? (I didn't indicate this in my drawing below)."

The shower will be wet vented by the washers vent. Since the distance between the trap and vent will be less then 3 1/2 feet 1 1/2" is acceptable but not advisable.

"regarding running traps, is there any "vertical feed" requirement to make them work? E.g. should there be a drop of X inches for a 2" pipe before entering the trap?"

By "vertical feed" are you referring to a vent? No vent's required on so short a run. 1/4" to the foot is normal slope.

" will the washer drainage siphon out my shower's "running trap" in the setup I've described? "
Here's where we run into a problem. Not with the seal being "sucked" out of the trap but with the discharge from the washer backing up into the shower.
I meant to bring this up earlier but it slipped my mind. My concern is that with the washers pump discharging with the force and volume that it does plus the fact that the shower's so close and so much lower that even the slightest partial blockage will send all the washer discharge back through the shower drain.
This is a very real concern and the only way I can see around it would be to install a swing check valve after the trap.

"Why is a "running trap" illegal in some places and not other?"
This is a local code issue since they aren't outlawed in my Standard Plumbing Code Book.

As I've stated, my only concern is the washer backing up into the shower.
And your thoughts? Regards, Tom

HI speedball-Tom:

There is about 8 ft of horizontal from the washer to the drain/vertical pipe. And the drain is 2" vs. the 1-1/2" from the washing machine. The plumbing all drains very effectively and it's a fairly new house construction (10 yrs). And finally the shower will be raised I'm thinking at least 8" above the floor which means only 5" or 6" below the washing machine Tee. Instinctively I would be surprised if the water coming down the pipe would have enough force and/or find an easier path up the drain to the shower than straight down the drain, but then what do I know..

This check valve -- it sounds like it would carry a higher risk of getting plugged, so I'd have to balance the probability of the washer draining up into the shower vs. the probability and hassle of the check valve getting plugged... what do you think?

Regards,
neophyte-Tom

I err on the side of caution. It would depend on the distance between the shower connection and the base of the vertical pipe as to the possibility of the washer backing up into the shower and this I don't know. The check valve was just off the top of my head and probably wasn't the best idea I've ever had. Regards, Tom