Adding washer standpipe and vent

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Brandon Huber

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Hello fine folks. I'm hopeful that I've posted this in the right section as I'm looking for a little help with some plumbing changes I'd like to make in my laundry room and I live in BC Canada. I've read countless other threads but none seemed to be exactly the same as mine. Anyhoo... So currently I have a large concrete laundry sink that drains into a 2" drain stack. Straight above is the kitchen where the sink also drains into the same line so I guess the laundry sink is wet vented. We have a washing machine that drains into the concrete sink and has left the surface of the concrete all pitted and nasty. The diagram below shows the current set up:
Laundry plumbing current.png


So, what I'd like to do is add a branch with a stand pipe for the washing machine. I'd stack the washer and dryer and replace the sink with one mounted into a base cabinet. Because there is a window over the sink I want to run all the plumbing inside the cabinet so I'm not drilling any studs; this limits the height of my venting. I realize that the washer's drain will need it's own vent so, when I remodeled the upstairs I thought to tie in a 1 1/2" abs line in the wall near the ceiling and ran it straight down into the closet below. It's currently hidden in the closet with a cap on it ready to use. So I'm wondering if I can simply bring it down low enough to fit in the back of my proposed sink cabinet and tie it in at some point? I tried to draw it out below. Also wondering if it's okay to leave the sink wet vented as it is currently. For reference the drain from the sink will be about 3' from the stack and the standpipe would be about 7' from the stack. Any help much appreciated!
laundry plumbing proposed.png
 

Reach4

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I am not a plumber. If keeping the laundry sink in place vented from the kitchen above due to grandfathering, I think you would need to bring the standpipe drainage in below the laundry sink drainage.

If on, the other hand, you don't rely on grandfathering the laundry sink, I think you should vent both p-traps before the drain stack. That could be with a real vent, as you propose, and that is best. It could also be with an AAV that is 6 inches higher than the flood level of the standpipe (the higher of the two). The AAV could be shared, or each could have its own AAV.

My comments are not based on BC code, but on an Ontario discussion. I am guessing BC is not more stringent than Ontario.

I would suggest that you add a cleanout above your new santee. The place that pipe system is likely to clog is below the drain stack in your picture, at the place where the flow turns from vertical to horizontal under the basement floor. A wye with a cleanout plug would be very good, and would get the snake going the right direction, down.
 

Brandon Huber

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Ok, that's helpful thank you. So, if I want to vent the laundry sink trap as well can I just tee the same vent line that's going to the standpipe like this?

laundry plumbing proposed2.png


Or, so I need to tee the vent line higher than the standpipe like this?

laundry plumbing proposed3.png


Either way it seems likes it's going to be quite a mess of pipes - any way to do it more efficiently? Again, thanks for any help!
 

wwhitney

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A dry vent needs to rise to 6" above the associated fixture overflow level before turning horizontal or joining another vent. So raise the orange horizontal to the top of the red segment, and just join them immediately, no need for that little red/orange loop.

Cheers, Wayne
 

Brandon Huber

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A dry vent needs to rise to 6" above the associated fixture overflow level before turning horizontal or joining another vent. So raise the orange horizontal to the top of the red segment, and just join them immediately, no need for that little red/orange loop.

Cheers, Wayne

Argh, that’s what I was afraid of. I was hoping that I could hide the vent lines in the back of a sink cabinet but obviously that won’t work. It’s a 2x4 exterior wall with a window in it so I won’t be drilling any studs to run pipes horizontally. I guess my only option is to fur out the wall an extra 2” or so. Does that sound like the best plan?
 

wwhitney

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Drilling the king stud for a vent pipe might be nice to avoid. But the vent only has to be 1-1/2", and at least in many places in the US, it would be fine to drill 2x4s for that and reinforce them with a metal bracket. My preferred brackets would be Simpson Strongtie's HSS series.

A few other things that may help you avoid furring out the wall:

The vent take off has to be within a certain distance of the trap, and before the trap arm falls more than one pipe diameter from the trap outlet. You can look up the distance in your plumbing code; in the US for a 2" trap arm, it would be 60" for one of our codes (UPC), or 96" for the other (IPC).

45 degrees off vertical is still considered vertical.

So you could move the orange vent take off as far to the left as possible, and then turn 45 degrees to the left immediately, and maybe you'd be able to
get past the window before rising above the top of the countertop.

Or you could move the vent takeoff far to the right, and then immediately start jogging right, and try to get around the window that way.

Lastly, if your plumbing code allows AAVs, you could use an AAV.

Cheers, Wayne
 

Brandon Huber

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Drilling the king stud for a vent pipe might be nice to avoid. But the vent only has to be 1-1/2", and at least in many places in the US, it would be fine to drill 2x4s for that and reinforce them with a metal bracket. My preferred brackets would be Simpson Strongtie's HSS series.

A few other things that may help you avoid furring out the wall:

The vent take off has to be within a certain distance of the trap, and before the trap arm falls more than one pipe diameter from the trap outlet. You can look up the distance in your plumbing code; in the US for a 2" trap arm, it would be 60" for one of our codes (UPC), or 96" for the other (IPC).

45 degrees off vertical is still considered vertical.

So you could move the orange vent take off as far to the left as possible, and then turn 45 degrees to the left immediately, and maybe you'd be able to
get past the window before rising above the top of the countertop.

Or you could move the vent takeoff far to the right, and then immediately start jogging right, and try to get around the window that way.

Lastly, if your plumbing code allows AAVs, you could use an AAV.

Cheers, Wayne

Wow, some great advice here thank you! Now that I know that it is possible to run the vent line at 45 degrees it looks like I can have the vent concealed behind the cabinets and stay below the countertop. I think I'm leaning towards running the vent down to the trap arm for the new standpipe while relying on the current wet venting for the laundry sink. Is this a bad idea?? It's worked for 60 years - but I wonder if the water entering the stack from the washing machine will be able to suction the sink trap dry. hmmm
 

wwhitney

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The US codes consider it a bad idea, and while it may have worked for 60 years, you are adding to the system, so it may not keep working.

A vent that turns horizontal below the usual level (6" above the flood rim) is better than no vent at all. One of the US codes allows it when structural conditions preclude the usual rise. And in that case the portion of the vent below the usual level is required to be plumbed following the rules for drainage.

Cheers, Wayne
 
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