Laundry sink relocation

[Net_Tech]

Hi,

I need to move a laundry sink to the left, the drain has to be right next to the stud (red arrow is showing where it needs to go)
Am I gonna create any problems by cutting the sink drain arm and making it shorter than 3 inches?

Would I create even more problems if I put two 45 elbows on the vent to offset the whole stack ?

Thank you

 

[John Gayewski]

It doesn't look like you can move the stack because thre fittings are already back to back. If you offset over 45 you must also go up 45. If you go up the lav won't have a vent.

You could move the stack if you also revented the lav and raised the standpipe. But i think you would also run out of elevation for the laundry sink.

 

[Sponsor]

 

[John Gayewski]

Hi,

I need to move a laundry sink to the left, the drain has to be right next to the stud (red arrow is showing where it needs to go)
Am I gonna create any problems by cutting the sink drain arm and making it shorter than 3 inches?

View attachment 81395

Would I create even more problems if I put two 45 elbows on the vent to offset the whole stack ?

View attachment 81396

Thank you

3" trap arm should be fine think. The min i belive is twice the pipe diameter. There is a chance that suds from the washer and water from the lav could effect your trap seal. But i would be curious on this one and not confident that they would.

 

[Jeff H Young]

I see no problem offsetting the vent ? your talking about putting a 45 on top of the santee for the Lav? no harm there. and cutting the dirty arm to your laundry sink nothing wrong with that either, BTW you need a min 2x pipe diameter distance edge of vent to trap weir . that doesn't mean your glue piece needs to be 3 inches there is a 90 plus its sticking out the wall . you could glue your 90 hub to hub with the santee no problem

 

[Net_Tech]

It doesn't look like you can move the stack because thre fittings are already back to back. If you offset over 45 you must also go up 45. If you go up the lav won't have a vent.

You could move the stack if you also revented the lav and raised the standpipe. But i think you would also run out of elevation for the laundry sink.

Thanks John!

I can cut the stack out and put a new one in with an offset if that does not cause any issues. I have access to the drain pipe going to the basement.

The only question is can the vent be offset, which would give me a few inches to make the laundry sink drain at least 3 inches.

Let me get all fittings and take a picture of what I intend to do.

 

[Net_Tech]

I see no problem offsetting the vent ? your talking about putting a 45 on top of the santee for the Lav? no harm there. and cutting the dirty arm to your laundry sink nothing wrong with that either, BTW you need a min 2x pipe diameter distance edge of vent to trap weir . that dosent mean your glue piece needs to be 3 inches there is a 90 plus its sticking out the wall . you could glue your 90 hub to hub with the santee no problem

This is what I mean by offsetting the vent. Do I have to be at a certain height for the offset from the water line or two 45 can go right on the top of the stack?

Thank you!

 

[Reach4]

Dry vents can split/join 6 inches or more above the flood level of the fixtures served.

A vent line has to stay vertical (within 45 degrees of plumb) until 6 inches above the flood level...

 

[wwhitney]

Why do you want to offset the vent?

The trap arm minimum length counts all the pipe outside the wall, it goes from the trap to the san-tee. So you'll (almost) never end up too short with an external trap and a san-tee inside the wall. Certainly not with an elbow in the trap arm.

BTW, the 3 stacked san-tees does not comply with the IPC's wet venting rules. The IPC limits vertical wet venting to bathroom groups, and the allowance for common venting only applies to 2 fixtures, not 3 fixtures.

Cheers, Wayne

 

[Net_Tech]

Dry vents can split/join 6 inches or more above the flood level of the fixtures served.

A vent line has to stay vertical (within 45 degrees of plumb) until 6 inches above the flood level...

Thank you!

So if I do something like this to offset the vent, I am not violating any plumbing codes?
1.5 inch pipe in the picture is only used for illustration, if I can go this route to offset the vent i will be using a 2 inch pipe to get above the 6 inch flood level.

 

[Net_Tech]

Why do you want to offset the vent?

The trap arm minimum length counts all the pipe outside the wall, it goes from the trap to the san-tee. So you'll (almost) never end up too short with an external trap and a san-tee inside the wall. Certainly not with an elbow in the trap arm.

BTW, the 3 stacked san-tees does not comply with the IPC's wet venting rules. The IPC limits vertical wet venting to bathroom groups, and the allowance for common venting only applies to 2 fixtures, not 3 fixtures.

Cheers, Wayne

@wwhitney

The reason to offset the vent is to get the sink 90 elbow as close to the stud as possible, the stud is actually the center of the cabinet. So the end result looks like this

The house was built (2005) with a stacked 3 san tees, there were no modification to the laundry plumbing as far as I know.
Was the code for the number of san tees that could be stacked changed recently?

Thank you!

 

[Reach4]

No problem jogging the vent 45 degrees as you show it.

If the bottom santee were fed by something already vented, probably no problem. But it is not. So problem meeting code. Could you fit an AAV in, with a vented access panel on the laundry standpipe trap arm just to the left of the santee? Needs to be 4 inches up from the trap arm but have enough space to change the AAV if needed.

From https://www.iccsafe.org/building-sa...ps-in-the-2021-international-plumbing-code-2/

 

[Net_Tech]

No problem jogging the vent 45 degrees as you show it.

If the bottom santee were fed by something already vented, probably no problem. But it is not. So problem meeting code. Could you fit an AAV in, with a vented access panel on the laundry standpipe trap arm just to the left of the santee? Needs to be 4 inches up from the trap arm but have enough space to change the AAV if needed.

From https://www.iccsafe.org/building-sa...ps-in-the-2021-international-plumbing-code-2/

Are you saying the code is already violated because I have 3 san-tees on a single wet vent, and the solution to the violation is to add an AAV for the washer?

 

[wwhitney]

If the sink is centered, then I agree that having the trap adapter within one u-bend c-t-c diameter of center simplifies the under sink plumbing. Have you look at rotating the san-tee and just using a 45?

I don't know what code was in force when your house was built, but I glanced at the relevant portion of the 2003 IPC and it appears to be the same as currently. There's also another violation, of 406.2, which says that when the laundry standpipe drain joins another drain, the combined drain needs to be 3". That's also in the 2003 IPC.

Are you saying the code is already violated because I have 3 san-tees on a single wet vent, and the solution to the violation is to add an AAV for the washer?

Basically. The top two san-tees can use the vent above, but the 3rd (bottom) fixture needs a separate vent. That could be an AAV, or it could just be a revent in the wall.

The tricky thing is how to do the revent without having pipes cross over each other in the wall. If you are going to redo the stacked san-tees anyway, you could do this: The laundry standpipe looks very long, so it could be shortened, so that the laundry connects to the middle san-tee. Then the bottom san-tee side entry, going up stream, hits a LT90, a san-tee for the laundry sink, and the revent rises and joins the stack at 6" above all 3 fixture flood rims.

Instead of a san-tee and LT90 at the bottom, you could use a wye and a 45, but that would require a diagonal hole in the stud. Also, if you really want the laundry sink stub out to be right next to the stud, you could put the LT90 on the right side of that stud bay, having your san-tee point to the left, and then put your stub-out where you want it. Or as I mentioned, turn the san-tee 45 degrees and use a 45, with the LT90 on the left side of the bay.

Cheers, Wayne

 

[Net_Tech]

If the sink is centered, then I agree that having the trap adapter within one u-bend c-t-c diameter of center simplifies the under sink plumbing. Have you look at rotating the san-tee and just using a 45?

I don't know what code was in force when your house was built, but I glanced at the relevant portion of the 2003 IPC and it appears to be the same as currently. There's also another violation, of 406.2, which says that when the laundry standpipe drain joins another drain, the combined drain needs to be 3". That's also in the 2003 IPC.


Basically. The top two san-tees can use the vent above, but the 3rd (bottom) fixture needs a separate vent. That could be an AAV, or it could just be a revent in the wall.

The tricky thing is how to do the revent without having pipes cross over each other in the wall. If you are going to redo the stacked san-tees anyway, you could do this: The laundry standpipe looks very long, so it could be shortened, so that the laundry connects to the middle san-tee. Then the bottom san-tee side entry, going up stream, hits a LT90, a san-tee for the laundry sink, and the revent rises and joins the stack at 6" above all 3 fixture flood rims.

Instead of a san-tee and LT90 at the bottom, you could use a wye and a 45, but that would require a diagonal hole in the stud. Also, if you really want the laundry sink stub out to be right next to the stud, you could put the LT90 on the right side of that stud bay, having your san-tee point to the left, and then put your stub-out where you want it. Or as I mentioned, turn the san-tee 45 degrees and use a 45, with the LT90 on the left side of the bay.

Cheers, Wayne

Wayne,

All this is very helpful! Let me try what to suggested to see what would be the best option. Currently, washing machine box sits way too high with a stand pipe being 36 inch tall. I do want to shorten it by at least 10 inches so the new box is at 40 or 41 inches from the floor.

When you say "rotating the san-tee and just using a 45" Do you mean rotating 180 degrees to the left so the inlet points to the left? Not sure I understand how it's gonna work out.

 

[wwhitney]

The "rotating the san-tee 45 degrees comment" was initially in reference to your first photo. I.e. instead of having the san-tee opening point towards the stud, with the trap arm going through a hole in the stud and then hitting an immediate 90 to exit the wall, turn the san-tee 45 degrees CW from above. Then put a street 45 in the outlet, and it would still exit the wall, just to the left of the stud or partially in front of the stud.

The same idea applies if the san-tee ends up on the right side of the stud, just pointing the side inlet out and to the left, with a street 45 to be perpendicular to the wall.

Cheers, Wayne

 

[wwhitney]

I do want to shorten it by at least 10 inches so the new box is at 40 or 41 inches from the floor.

That should be a good height, just double check your washer manual for what is allowed. There could be some washers which if installed on a pedestal need to be higher (not sure if that's true or not, but it's possible).

Cheers, Wayne

 

[Net_Tech]

The "rotating the san-tee 45 degrees comment" was initially in reference to your first photo. I.e. instead of having the san-tee opening point towards the stud, with the trap arm going through a hole in the stud and then hitting an immediate 90 to exit the wall, turn the san-tee 45 degrees CW from above. Then put a street 45 in the outlet, and it would still exit the wall, just to the left of the stud or partially in front of the stud.

The same idea applies if the san-tee ends up on the right side of the stud, just pointing the side inlet out and to the left, with a street 45 to be perpendicular to the wall.

Cheers, Wayne

Got it!

Actually this way I don't need to offset the vent and the sink drain is right in the center of the cabinet.