Add laundry sink to washing machine plumbing question

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KettleKorn

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Hi,

I'm moving my washer/dryer from inside the home to the garage. As of now, they are on the opposite side of the garage wall. I'd also like to add a laundry sink as well. I'm running into 2 problems.


Height problem:
The garage sits 6 inches lower than the house foundation slab. But the drain comes out of the raised house slab. It looks like the laundry drain is going to be sitting pretty high. My laundry sink bottom sits 19.5 inches from the ground (with legs extended maximum height.) I guess I could put it on blocks or something to raise it up if needed.

Width problem:
I can only go 22 inches to the left of the current drain before I hit a load bearing wall that intersects with this wall. (I've been in the attic to check.) I don't want to go more to the right as I'm putting a door in that direction, plus the laundry sink will go near there.

Here's what I have currently.
Current cast iron is 2 inches, the vent is 1.5 inches. I would cut the existing and connect via fernco fittings.
IMG-2673.jpg




Here's what I'm thinking of doing. Everything new will be 2 inch ABS, including the venting.
IMG-2673a.jpg



Questions:
#1 Can I move the new cleanout from the base of the stack to somewhere higher? This would allow me to move the Double Fixture Tee a little lower so I can lower the height of where the horizontal runs come out, this lowering the P-traps on both sides.

#2 What is the minimum on the horizontal piping sections for the washing machine, with yellow labels A and B on the second photo, I already measured with 4 inch piping sections on both A and B, and assembled with P-trap, combo for vent, and double fixture tee, that's already at least 3 inches too long. Ideally, I'd like to cut the piping to slam the fittings together, similar to this:
IMG-2680.jpg



I'm located in California, btw.


Thanks in advance.
 

wwhitney

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0) Your laundry standpipe trap has to be 6" to 18" above the garage floor.

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/8/indirect-wastes#804.1

1) Sure, move the cleanout above the fixture drains, rather than having it below.

2) You don't need to revent the laundry standpipe if using a double fixture fitting. I'm not sure that the double fixture fitting is a good idea, but I also don't think it is disallowed. More typical would be vertically stacked san-tees, with the laundry standpipe on the lower san-tee, and the laundry sink san-tee just above it. That's an allowable vertical wet vent (the opposite order would require reventing the laundry sink).

Cheers, Wayne
 

KettleKorn

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0) Your laundry standpipe trap has to be 6" to 18" above the garage floor.

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/8/indirect-wastes#804.1

1) Sure, move the cleanout above the fixture drains, rather than having it below.

2) You don't need to revent the laundry standpipe if using a double fixture fitting. I'm not sure that the double fixture fitting is a good idea, but I also don't think it is disallowed. More typical would be vertically stacked san-tees, with the laundry standpipe on the lower san-tee, and the laundry sink san-tee just above it. That's an allowable vertical wet vent (the opposite order would require reventing the laundry sink).

Cheers, Wayne


Thanks for the info. I'll move the cleanout further up to save some vertical space for the double fixture. Do you know if I can space the washing machine horizontal run closer together like in the last photo?
 

wwhitney

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The last photo shows a dry vent takeoff via a combo on the washing machine trap arm, which isn't required, so I don't follow the question.

If the trap outlet goes directly into a san-tee which is venting the trap, the minimum trap arm length requires about one pipe diameter (2" for the washing machine) worth of visible pipe between the san-tee hub and the trap outlet hub. (It's a bit under one pipe diameter, but I forget the details, so one pipe diameter is sufficient).

Cheers, Wayne
 

KettleKorn

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Hi Wayne,

I should've made myself more clear. Sorry about that. So in this image below, I have A & B marked.
IMG-2673a.jpg


From what I understand, the distance between the P-trap and the vent (Section A) must be twice the distance minimum, so 4 inches as it's 2 inch pipe. I believe.

Is the same required for Section B which is between the vent and stack? So that must be minimum 4 inches too?

Thanks!
 

wwhitney

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The rule is that the trap arm has to be at least 2 pipe diameters in length. The trap arm starts at the trap weir (point at which water first spills out of the trap when you start filling an empty trap) and ends at the edge of the vent opening at the top of the pipe. So with the combo providing the (unnecessary) vent as in your photo, it's the distance between the green lines in the markup below.

There's no length requirement on the section downstream of the vent.

Cheers, Wayne

TrapArmLength.jpg
 
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