Ask Me Help Desk - Plumbing a laundry in a duplex

I'm looking for help in plumbing a laundry in a duplex. I need to add two washers and a laundry tub. There is an existing 1 1/2" vented drain about 24" away that was connected to an old concrete laundry tub - I plan to use that for the new laundry tub.

For the washing machines, I know I need to run 2" drains w/ p-traps and a 36" stand pipe. I have a 3" toilet drain approx 3' away that I could add on to the cleanout with a wye. Can I run both 2" washer drains into a single tee and then into the 3" drain? Also, that would be about 12" off the floor for the drain into the 3" pipe - do I need to carry the standpipe 36" above that point; or just above the washer lip?

Also, there is an existing 2" galvanized vent pipe that's been cut off directly above the spot for the washers. I can't see that anything else is attached to it. Can I use this to vent both of the washer drains?

Thanks for any help you can give me.

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Originally Posted by perovich

I'm looking for help in plumbing a laundry in a duplex. I need to add two washers and a laundry tub. There is an existing 1 1/2" vented drain about 24" away that was connected to an old concrete laundry tub - I plan to use that for the new laundry tub.

Well, the laundry tub should really have a 2" drain.

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For the washing machines, I know I need to run 2" drains w/ p-traps and a 36" stand pipe. I have a 3" toilet drain approx 3' away that I could add on to the cleanout with a wye. Can I run both 2" washer drains into a single tee and then into the 3" drain? Also, that would be about 12" off the floor for the drain into the 3" pipe - do I need to carry the standpipe 36" above that point; or just above the washer lip?

Well, your standpipe's can be as short as 18", if that helps.

As for connecting the two traps and trap-arms, if they are back to back or side to side, you could use a 2" Partition Cross, but a double sanitary tee cannot be used in this application -- A double san-tee is a vent fitting, not a drainage fitting.

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Also, there is an existing 2" galvanized vent pipe that's been cut off directly above the spot for the washers. I can't see that anything else is attached to it. Can I use this to vent both of the washer drains?

If you use the Partition Cross mentioned above, you can definitely take advantage of the 2" vent, but you need to make certain the vent is still tied in and functional.

Thanks for the info. I know the laundry sink should probably be a 2" drain as well; I could cap the existing drain and tie in to the new wash drains, but I don't expect a lot of use from it.

Also, instead of using the existing galzanized vent pipe could I use one of those self-sealing vent caps (that open to drain and then re-seal)? I thought of that because I'm really not sure if the galvanized pipe hasn't been cut somewhere above (this is in the basement of a three story 1906 house).

Thanks.

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speedball1 disagrees: Installing a 18 inch washer stand pipe is just asking for trouble with today's more powerful washer pumps. 36" of 2" pipe is the normal height

You're giving me a negative rating for giving advice that is in compliance with *ALL* of the prevailing Plumbing Codes adopted for use in the US, Tom?

>shakes head<

Considering the discussions we've had on this very topic in the past, that takes real balls, Tom.