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 Adding a laundry sink to an existing waste hub.
Author: specbebop (TX)

In the pictures below, I am adding a laundry sink to the left of the existing washing machine standpipe:

In these pictures, the vertical pipe to the right is a 2" vent to the roof with no other fixtures tying into into it.

To do so, I'm going to remove that cast iron p-trap, run a new 2" PVC pipe into the hub, then tie a new washing machine standpipe/p-trap and the the new laundry sink p-trap into that 2" PVC. I have two questions:

1) Do I need to add a new vent after the laundry sink p-trap and before the washing machine stand-pipe to prevent siphoning?

2) Any suggestions for separating that cast iron p-trap from the hub? They are joined using a donut (that is in very good condition).


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 Re: Adding a laundry sink to an existing waste hub.
Author: hj (AZ)

The first question that comes to mind is HOW are you going to install the washer "P" trap, and THEN continue on to the sink trap?

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 Re: Adding a laundry sink to an existing waste hub.
Author: North Carolina Plumber (NC)

You could just cut the standpipe, no hub a tee there and run PVC on up to the opening in the wall. No trap will be required on the laundry, nor will any other venting be required.

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 Re: Adding a laundry sink to an existing waste hub.
Author: NoHub (MA)

Those are some old push gaskets you have there.

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 Re: Adding a laundry sink to an existing waste hub.
Author: m & m (MD)

I would install the same as NC suggests but not all codes may approve of a "trap-less" laundry sink.

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 Re: Adding a laundry sink to an existing waste hub.
Author: packy (MA)

isn't it great to have so many opinions on a simple job..
my opinion.. support that galvanized vent stack and using a sawzall cut it about 2 feet from the floor.
remove everything down to the push gasket by the floor.
starting from the floor up.. put a short piece of 2 inch pipe, a 2 inch sanitary tee looking to the left, another short piece of 2 inch pipe, a 2 inch CLEANOUT TEE, another piece of 2 inch pipe all the way up to the cut at the galvanized vent and lastly a 2 inch no hub coupling to join the plastic and the vent.
believe me.. with cast iron under the floor, you will be happy to have a cleanout at some point in the future.
now, from the left of that san tee just put the 2 inch trap with a san tee in the standpipe looking over to the sink.
and since you have to cut the water lines to install tees and shut offs for the new sink, might as well install a plastic laundry box with nice new 1/4 turn hose valves. replace the hoses with stainless hoses.
now we are talking a CADILLAC ELDORADO first class job.

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 Thanks all for the suggestions. All great ideas :clap:
Author: specbebop (TX)

Thanks all for the suggestions. All great ideas. I should add that the laundry sink that I'm adding will, at the end of the day, be about 12' of developed pipe length from that existing galvanized vent. It's my understanding, with the 2012 UPC, that would be too far from the vent to do a trapless sink. But, I may be wrong.

I like your plan Packy. While I have the walls open, I'd prefer to do it right. And, yes plan includes replacing all of that old washer box mess. New box, new pex lines from the existing supply lines, new stainless hoses.

So, any advice for pulling all that cast iron out of the push gasket at the floor?

Thanks again.

Edited 1 times.

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 Re: Adding a laundry sink to an existing waste hub.
Author: packy (MA)

time out.. we need a new game plan..
12 feet is way to far. any suggestions were for a sink setting right next to the washing machine. then pipe it like it is a doubl bowl sink. 1 trap with a tee setting on it. washer into top of tee and sink into side..
so now you will have to put 2 san tees at the floor. one on top of the other.
the lower one will have a 1 1/2 inch branch looking to the left. the top one will be full size 2 inch but it will be about a foot above the lower one.
the 1 1/2 drain for the sink will run about 8 feet to the left. at that point put a 90 looking up. a short piece of 1 1/2 in the elbow with a 1 1/2 san tee on that. the san tee looks to the left and will pick up the sink trap. the top of that san tee will have a piece of pipe in it up to about 42 inches high. put a 90 on that looking back at the vent stack. then run that vent back and tie it into the laundry vent.
the washer piping remains the same.
as for the push gasket, don't be suprised if you have to destroy and get a new one. they are readily available and cheap..some liquid detergent will lube up the new push gasket so it will slide together easier..

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 Thanks again, Packy :grin:
Author: specbebop (TX)

Thanks again, Packy. I should've included the information about the distance between sink and vent in my original post.

Sounds like a good plan to me. And, I don't mind destroying that push gasket to get everything out. A quick search shows a new push gasket to be less that $10.

Edited 1 times.

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