I'm adding a second floor laundry in an unused closet. The space has an interior wall with an unused return air duct that goes straight down to the unfinished basement right next to the main house drains. Lucky, I know..

There are two places I can tap into the drain at the bottom of the duct. A 2" line and a 3" line. The 3" line connects directly to the main stack for the house and drains the master bath and shower that is on the second floor. The 2" line (I think) is the vent line from the sewer lines that run in the basement floor (the line goes down into the cement basement floor). The only drain I can find that goes directly into this 2" line is the full basement bath which is at the end of the duct I'm using to run the pipe.

From the location of everything, it would be MUCH easier to connect into the 2" line, but I'm assuming I do NOT want to do that since I'd run too great a risk of flooding the downstream basement bath. So I'm leaning towards tying into the 3" pvc for now.

Assuming that's correct, do I need any upstream vent for the new laundry drain since its draining into an already vented stack?

And where is the best place for the P trap for this drain? I'm leaning towards putting it at the end of the duct right before I connect to the 3" pvc. Everything above that will be essentially vertical, so there shouldn't be any standing water anyway.

If I'm missing anything else, please let me know. Thanks for all the help.

Mike

Here is my take on things... I am not completely clear on how basement ties into 2 " vent in basement or how 2" line enters basement floor without being a waste line.. BUT I do not think it matters... here is what I would do.

At 2nd floor closet I would install a washing machine box in the rear or side wall (if interior wall) . Then I would pipe a 2" p-trap directly out of the box with the first cut of pipe from box to p-trap equal to about 25-30 inches long...this is code (in my area it calls for 30 inches). The box should be located a good foot above the washing machine height.

Now, the p-trap should connect to the branch of a 2 " tee fitting and send a 2" waste line down from that tee into the duct work and send an 1.5 " (reduce out of 2" tee with a 2 x 1.5 inch flush bushing) vent pipe from the top of this tee up into the attic. The 1.5" vent will need to connect into the vent system in the attic OR it will have to increase to 2" PVC pipe just before exiting the roof by itself (terminates above roof 18-24" in my area). The 2" drain pipe will need to drop to the basement transitioning with a long sweep elbow to the horizontal pipe you will be connecting into. (NOTE here...that you will need to install a 2" dandy clean out fitting at the base of this 2" waste stack...say within 2 or 3 feet of the vertical). Then I would connect into the 3" drain line... period! (especially as I am not clear on vent/wastes in basement... ;) )

Hey, let me know if this helped by rating the answer below. Thank you and let us know if we can help anymore or if I have misunderstood completely... OR if you need clarification on anything I have presented. Good luck!

No, but you'll have to run separate vents for every fixture that's draining into the pipe that you're using to drain the laundry into. By using this pipe as a laundry drain you have changed it from a vent stack to a stack vent from the second floor bathrooms up to the point where it vents your laundry where it morphs back into a vent stack. You may not discharge a major fixture such as a toilet or washer past unvented fixtures. And you took away the second floor vents when you connected a washer station to their vent. Now this needn't be a big bummer. If local codes permit you could cap off the two bathroom vents and install AAV's(Air Admittance Vents) just behind the traps. That would clear you to use the stack for your washer set-up.
The trap should go directly under the 36" stand pipe which should not be over 5 to 8 feet away from the stack. More questions? I'm as close as a click. Regards, Tom

Guys,

Thanks for the advice - this is really helpful. I'm not sure I understand the vent situation either other than this -- the 2" stack does not flow water from any upstairs drain (I've tested them all). But it does flow water from the sink in the basement which is connected to one of the branches that feeds upstream into the 2". The 2" line I'm talking about was installed when we did an addition and the plumber roughed in the basement bath at the same time. I've since finished the bath and connected to the roughed in pipe he left me for that purpose. Assuming that 2" pipe is what it looks like -- a vent for the rest of the basement, but not a drain for anything upstream - did he do something wrong by putting the basement bath on the same line?

Tom, I'm going to tap into the 3" pipe so I'll avoid having to use the AAV's. MP2008 -- I think I've got a good handle on everything you've described, but here's a couple followups if you don't mind.

What schedule pvc do I need? I'd like to use lighter schedule to get some flexibility since this is going to be a real pain to work the pipe all over the place at the bottom of the duct.

I'd never heard of a long sweep 90 so I looked it up -- great idea for a long drain stack like this. But the route I think I need to connect to the 3" pipe has me needing to do a 90 right at the bottom of the duct into about a 20" horizontal, another 90 to about a 30" piece that will angle down at at least 45 degrees and then another 90 back to a new 3" T. Somewhere in there I'll find a spot for the cleanout too -- excellent idea. I think it will probably go in the angled downtube if that's kosher.

btw, I found my local codes online. The require the P trap to be 18-30"s from the top of the stack. Glad you caught that since I was planning on having it about 120"s away. I can make it whatever I want, is it better to have the stack 30" or 18 or does it matter for best high volume, sudsy flow out of a washer?

Thanks again guys,
Mike

To answer your questions... Schedule 40 PVC pipe... can be regular or cellularcore PVC pipe (cellular core being lighter and easier to work with). A long sweep 90 can also be a 45 degree fitting cemented into a street 45 degree fitting... also, if accessible every 90 degree turn (except base of stack) would be best made via a wye fitting and street 45 and end cleanout at all changes of direction if possible. If this is not reasonable, then add a cleanout wherever you can... so says code... not me... EXCEPT... easier to install now then have issues later. And.. don't forget the cleanout at the base of the stack.. this is the one every one gets excited about if it is not present!!

Let us know if any more questions.. all good advise.. all good people here! Good luck.

You lost me on one thing. You note to use the wye/street to yield a long sweep 90 with a build in cleanout (great idea), but not to do that at the base of the stack. But then you said not to forget the cleanout at the base of the stack. So I'm missing something here that's probably painfully obvious to someone who knows what they are doing.

To summarize where I think I need to be top to bottom:
-Washing machine box to 2" stack that is 18-30" long -- any preference here on length?)
-P trap (no cleanouts) to a horizontal 2" pipe about 10 inches long into stud space over duct
-Horizontal into a 2" T sending 1.5" vent line through reducer to existing vents in attic and 2" stack down duct
-90 long sweep at base of stack (no cleanout) into 20" horizontal 2"pipe
-Horizonal pipe into wye/street 45 combo with cleanout to a 30" 2" section angled down about 45 degrees
-Angled pipe into another wye/street45/cleanout combo into the 3" T for waste stack. (This works out really well since it gives me a new cleanout for the 3" waste stack itself, which doesn't have an accessible cleanout right now)

Based on this, I don't think I need another cleanout right at the base of the 2" stack, right? I certainly hope not anyway, since that cleanout would be in the ceiling of the downstairs bath and I'd rather not punch in an access panel for it. Since the other cleanout would be less than 2 feet away and pretty accessible, I should be fine, right?

Thanks again for the education here -- this is great!
Mike

If the other cleanout is only 2 feet away from the base of the stack and is readily accessible then you should install the dandy type cleanout there. It should be OK by code. Just be clear that a dandy type cleanout is absolutely required at the base of a stack... but there is play as to distance away from base of stack... as long as close.

And the 2" pvc out of the washing machine box should be between 30 and 36" (I say 30", speedball1 says 36"... I think... either should be good really... but no shorter).

Other than that... all sounds great. Let us know how it works out... and of course, do not hesitate if you need more clarification!