Moving Washing Machine Drain Question

[csebasti]

I've been wanting to move my washing machine drain and supply lines for a while and thought I might be able to take advantage of a water damage situation in the bathroom that shares a wall. Drywall in the bathroom is partially removed, exposing all the plumbing in the shared wall. I could easily add a new washing machine drain where I want it and tie into existing pipes. But, I'm clearly no expert here, knowing just enough to be dangerous I suppose. So I'm looking for some advise on the drain line. Supply lines are no issue. I'm in Washington State.

I'm pretty sure what I would like to do is not up to code based on my limited research. In the image below, blue are existing vents. Green is what I'd like to do to get the washer where I want it. But, I'd be making a vertical wet vent below the new washer drain (assuming that line is the WC vent), and I believe that would require the pipe to be 3" (or maybe 2.5"), but it is currently 2" above the 3" cleanout. This is on the first floor, on a slab so no crawl space or basement to get a look at those pipes below the floor. I also believe that I can't wet vent with a fixture not in the bathroom group, so that is a second reason this wouldn't be up to code if I understand correctly.

So, are my assumptions correct in that this would not meet code? If so, do I have any options? I'd really rather not cut out the slab and dig in order to add a new drain, especially since I don't know if the drain runs under the laundry room or under the bathroom.

 

[wwhitney]

My comments:

- The existing vent takeoff for the standpipe trap arm is a san-tee on its back. The UPC, used in Washington, requires that to be a combo.

- I agree that the 3" cleanout and 2" pipe above it certainly looks like a vent for the WC. But that implies a section of dry vent under the slab, which is not allowed. If you are curious, you could remove the cleanout and use a flexible snake camera to see what the 3" pipe is doing under the slab for the first foot or two.

- The only way to cure the above apparent deficiency is to reroute the lav drain to enter the 2" pipe above the cleanout. That would turn the underslab piping into a compliant wet vent, rather than a non-compliant dry vent. On the other hand, if it's been working fine for however many decades, there's an argument for leaving it be. Particularly unless you do some verification of the underslab configuration.

- The standpipe drain can't be part of any bathroom wet vent.

Is that a 2x6 wall? If so, you'd have the depth to have 2" pipes cross with stud bay (2" pipe = 2.375" OD; 2x6 = 5.5" depth). In which case the simplest option is simply to run the new standpipe trap arm across the existing 2" vent above the 3" cleanout, so it can connect back to the existing 2" standpipe trap arm. A 2" trap arm can be up to 60" long, so no problem there.

Note that in the existing configuration, the lav drain and the washer standpipe drain form a vertical wet vent. That is allowed as long as the pipe between the two san-tees is at least 2".

Cheers, Wayne

 

[Sponsor]

 

[csebasti]

My comments:

- The existing vent takeoff for the standpipe trap arm is a san-tee on its back. The UPC, used in Washington, requires that to be a combo.

Ah, yes, I remember seeing something about san-tees not being allowed in that orientation.

- I agree that the 3" cleanout and 2" pipe above it certainly looks like a vent for the WC. But that implies a section of dry vent under the slab, which is not allowed. If you are curious, you could remove the cleanout and use a flexible snake camera to see what the 3" pipe is doing under the slab for the first foot or two.

I just bought one of these cameras last week so I could get a look under there. Haven't had time to do it yet though since I'll need to move the washer/dryer to get access. But I will get to that in the next week or so.

- The only way to cure the above apparent deficiency is to reroute the lav drain to enter the 2" pipe above the cleanout. That would turn the underslab piping into a compliant wet vent, rather than a non-compliant dry vent. On the other hand, if it's been working fine for however many decades, there's an argument for leaving it be. Particularly unless you do some verification of the underslab configuration.

Yep, it's been working for 40+ years. I think given that I don't want to mess with it if I don't need to.

- The standpipe drain can't be part of any bathroom wet vent.

Thanks for confirming that. That's what I thought.

Is that a 2x6 wall? If so, you'd have the depth to have 2" pipes cross with stud bay (2" pipe = 2.375" OD; 2x6 = 5.5" depth). In which case the simplest option is simply to run the new standpipe trap arm across the existing 2" vent above the 3" cleanout, so it can connect back to the existing 2" standpipe trap arm. A 2" trap arm can be up to 60" long, so no problem there.

Yes, this is a 2x6 wall. That sounds great, except for one thing. The 3" cleanout and 2" vent above it are right in the middle of the wall, not leaving enough room to get a second 2" pipe past it. But I suppose with a handfull of 22.5° elbows I could push the 2" vent back so that the new washer drain could get past. Doing this, I would not need the new trap I show, right? I'd just use a standpipe down to a 90° elbow to a horizontal run to a san-tee into the old standpipe above the trap?

Note that in the existing configuration, the lav drain and the washer standpipe drain form a vertical wet vent. That is allowed as long as the pipe between the two san-tees is at least 2".

Cheers, Wayne

Yep, it's 2" below the lav. 1.5" above the lav until until the upper horizontal vent hits it, then goes 2" up to the 2nd floor.

Thanks for the help. I think I have a solution here that will work.

Chris

 

[Jeff H Young]

Im thinking that below the 3 inch clean out is a 3 inch santee pointed over for the toilet . sure you can have a dry vent for a toilet underslab thats verticle ? Of cource it could have been vented wrong . looks pretty normal way to plumb a toilet .
Why not extend the trap arm on the washer (change the illegal santee on back if youy choose to do it right)? if you have to offset the 2 inch vent from the toilet so the trap arm can cross so be it , 2x6 wall should be piece of cake

 

[wwhitney]

Im thinking that below the 3 inch clean out is a 3 inch santee pointed over for the toilet . sure you can have a dry vent for a toilet underslab thats verticle ?

Yes, that would be compliant; I didn't consider that possibility. If the OP uses a camera we'll find out if that's the configuration. It would drop the WC drain down farther below the slab.

And actually, if that is the configuration, then the laundry trap arm can drain into the the 3" line coming up from the slab. The UPC allows any two fixtures to be vertically wet vented. So the 3" line could be extended up above the cleanout with a san-tee for the standpipe trap arm, then a 2" dry vent above that.

Thanks, Wayne

 

[wwhitney]

Thanks for confirming that. That's what I thought.

So I misspoke; that's only true for a horizontal wet vent. Per my previous post, if Jeff is right about what is under the slab, you can drain the standpipe into the 3" portion of that riser.

Doing this, I would not need the new trap I show, right? I'd just use a standpipe down to a 90° elbow to a horizontal run to a san-tee into the old standpipe above the trap?

No, you'd always want the trap under the standpipe, and all of the horizontal portion downstream of the trap.

Cheers, Wayne

 

[Jeff H Young]

My first observation I expect the toilet has a verticle dry vent I thought wet venting 908.1 limits the discharge to 1 and 2 fixture units and a clothes wasaher was 3 dfu?
Let us know Wayne as I am a little fuzzy on the clothes washer to w/c vent , might be a help in future

 

[wwhitney]

My first observation I expect the toilet has a verticle dry vent I thought wet venting 908.1 limits the discharge to 1 and 2 fixture units and a clothes wasaher was 3 dfu?

Darn, you're right. I forgot that 2 DFU limit, so scratch my idea. Good thing you're paying attention to this one. : - )

Cheers, Wayne

 

[Jeff H Young]

glad you looked too I wasent that sure I read it right its worded funny .

 

[csebasti]

Thank you all for the replies and suggestions. I don't have time to absorb it all right now, but will read it more thuroughly and break out the camera next week to to take a look down below the 3" cleanout and see what's going on under slab.

 

[csebasti]

Ok, I have some time to read though all the comments again. I have not had a chance yet to get the flexible snake camera out yet and open up that cleanout, but should be able to this weekend and see what is down below that 3" cleanout.

So it sounds to me like the conclusions, not knowing yet waht is under the slab, are:
- I will need to remove the existing standpipe and trap, and run a horizontal line over to the new standpipe and trap.
- I will need to offset the 2" vent above the 3" cleanout in order to get the new horizontal run past it.

I'm assuming there is no way, or at least no easy way, to remove a glued ABS pipe from a fitting. Looking at where I can plumb in the new pipe, it looks like I can cut out the santee on it's back and have enough room to put on a hub and run the new trap arm out to the left. I could move the washer vent over one stud cavity and put in a combo instead of the santee on it's back. Or is it ok to have the vent around 40-45 inches away from the standpipe?