Adding laundry sink, need advice for drain. Much appreciated!

[Ginsa]

Hi All,

First - thank you in advance for your reply!

I am adding a laundry sink and wanted to get some advice on how I can add the drain into the existing washer drain pipe. The standpipe for the washer drain has a trap close to the floor that connects to the big drain pipe for the house. I added a picture and a diagram to help explain.

My questions:
- Is the pipe in the middle the vent pipe? I'm not really sure about this, but the pipe goes up to the ceiling
- Where can I add the new drain pipe from the laundry sink? Can I add it to point (a) as in the diagram? Or do I need to add it to somewhere like point (b)?
- Do I still need a p-trap for the laundry sink if I can connect at point (a)? since there is a trap already downstream.

Thank you again!

 

[Diehard]

Hi All,

First - thank you in advance for your reply!

I am adding a laundry sink and wanted to get some advice on how I can add the drain into the existing washer drain pipe. The standpipe for the washer drain has a trap close to the floor that connects to the big drain pipe for the house. I added a picture and a diagram to help explain.

My questions:
- Is the pipe in the middle the vent pipe? I'm not really sure about this, but the pipe goes up to the ceiling
- Where can I add the new drain pipe from the laundry sink? Can I add it to point (a) as in the diagram? Or do I need to add it to somewhere like point (b)?
- Do I still need a p-trap for the laundry sink if I can connect at point (a)? since there is a trap already downstream.

Thank you again!View attachment 19421 View attachment 19422

You CANNOT add it to point (a) as in the diagram.
Point (b) would be okay, provided you added a vent for that trap arm from the sink trap. Refer to this chart for max. trap arm length from trap weir to vent.
https://www.plumbingforums.com/threads/true-sizes-for-abs-and-pvc-pipes.13196/

 

[frodo]

View attachment 19423

 

[Diehard]

But it would exceed 6' based on his sketch that shows that the sink trap is "about 6 ft horizontal" from the existing standpipe.

 

[Zanne]

Ginesa, as a general rule, you don't have a trap without a vent (unless you are wet-venting) and you will tie in to the drain of another fixture after the trap. Also, the standpipe P-trap must be at least 6" above the floor but no more than 18" above the floor. If it is less than 6" above the floor, it needs to be raised. Additionally, the top of the standpipe can be no lower than 18" above the P-trap but no higher than 30" above the P-trap (UPC) or 42" (IPC).
Example showing code rules in purple and red.

Frodo, what about this?
Goes up to vent between 4" to 5' and ties in to the vent while drain goes below standpipe and merges with larger drain? Vent 90 for top vent elbow, but long sweep for the drain part.


Or the drain could be higher and merge with the standpipe drain as you've shown. It could either have a long sweep to go 90 degrees down or it could have smaller bends to get it to the right angle for a wye.


Another way would be to keep the trap arm straight and have a sanitary tee on it's back (which is about the only time you can use one horizontally) to direct airflow up to the vent and the drain continues horizontally where it either meets the main drain or goes down to the standpipe's drain (after the trap).

Personally, I think going to the main drain is better. Depending on how much space you have, you could tie in either above or below the washing machine's P-trap. But I defer to Frodo & the other plumbers here.

 

[frodo]

View attachment 19425

 

[Zanne]

Frodo, I was just reading something that said if you tie something else in to the horizontal drain for a washing machine that the horizontal drain needs to be a minimum of 3" diameter. Is that correct?

What size drain do laundry sinks have? Are they 2" or 1-1/2"? I was assuming the latter- hence no more than 5' recommendation. But, if it's 2" then it would be 6', right?

Also, is my drawing #3 close enough? (My drawing sucks, but it's supposed to be a combo wye where it ties in).

 

[frodo]

[QUOTE


Frodo, what about this?
Goes up to vent between 4" to 5' and ties in to the vent while drain goes below standpipe and merges with larger drain? Vent 90 for top vent elbow, but long sweep for the drain part.
View attachment 19426

Or the drain could be higher and merge with the standpipe drain as you've shown. It could either have a long sweep to go 90 degrees down or it could have smaller bends to get it to the right angle for a wye.
View attachment 19427

Another way would be to keep the trap arm straight and have a sanitary tee on it's back (which is about the only time you can use one horizontally) to direct airflow up to the vent and the drain continues horizontally where it either meets the main drain or goes down to the standpipe's drain (after the trap).

Personally, I think going to the main drain is better. Depending on how much space you have, you could tie in either above or below the washing machine's P-trap. But I defer to Frodo & the other plumbers here.[/QUOTE]


The laundry tub drain height is going to dictate how you rough in a drain
if it is one of those stand along laundry tubs. that sits on 4 legs. I think the drain rough in is around 9''
from floor to center of drain.
set up the laundry tub, connect a trap. then measure floor to center line trap outlet.
Then subtract 1 1/2'' [1/4'' fall @6']
this will give you your center line height measurement for take off from main drain

I am in agreement going to the main 3'' waste stack is the best way to go
IF, the existing tee is not in the way. IF it is, then you will have to cut out everything and repipe both washer and sink

 

[frodo]

Zanne
Frodo, I was just reading something that said if you tie something else in to the horizontal drain for a washing machine that the horizontal drain needs to be a minimum of 3" diameter. Is that correct?

I am not aware of that, a 2'' horizontal branch is maximum 6 fixture units
a domestic washer is 2, a laundry tub is 2 a 2'' line is good to go


What size drain do laundry sinks have? Are they 2" or 1-1/2"? I was assuming the latter- hence no more than 5' recommendation. But, if it's 2" then it would be 6', right?
I believe in the funky IPC 6' is allowed on a 1 1/2'' arm...
2'' is 8'

 

[Zanne]

Thanks, Frodo. When I was looking it up it was mentioned by people in Ohio so maybe it's just the code there.
I'll have to look at the IPC codes again. Not sure if Ginsa uses UPC or IPC (and oops, misspelled the name upthread).

I do think that if the trap is less than 6" from the floor it should be raised up anyway. Given that the trap arm might start at 9" above the floor and drops a full inch after 4' then it drops 2" after 8'- and it seems to be greater than 8' distance-- it would put maybe between 6" to 7" above the floor when it passes the standpipe P-trap. So, moving the standpipe P-trap up to maybe 10" or 12" might give the other pipe clearance underneath.

I hope I'm making sense.

not sure if any bends would be necessary to get it to the right spot or not.

 

[Diehard]

Maryland code is shown as being the IPC according to this list...

https://www.plumbingforums.com/threads/plumbing-code-by-state.5654/

This is not entirely true but close enough.

I don't believe this requirement, "the standpipe P-trap must be at least 6" above the floor but no more than 18" above the floor.", is included in the IPC.

Regarding the statement/question, "I was just reading something that said if you tie something else in to the horizontal drain for a washing machine that the horizontal drain needs to be a minimum of 3" diameter." I believe this would be the case when using one of the newer High Volume washing machines that exceed the listed DFU's. Whether the code mentions it or not!

Here's an interesting requirement in the 2018 IPC...


So now, I believe, we have the option to move the existing standpipe closer to the laundry sink to meet the above requirements.
Whaddaya think?

EDIT:
Definition of laundry tray: a fixed tub (as of slate, earthenware, soapstone, enameled iron, or porcelain) with running water and drainpipe for washing clothes and other household linens
— called also set tub

 

[Ginsa]

Wow! Thank you everyone so much for the detailed responses!

Zanne, I don't think the current p-trap is 6 inches off the floor, but I will move the washer out to check later. It just looked like it was maybe just 3 inches above. And as such, the standpipe drain is connected to the waste stack pretty close to the floor as well.

I was actually hoping to connect the sink's drain into the standpipe's drain as in Zanne's #3 drawing, since that seemed like it was simpler. But if the current p-trap needs to be raised then I think I will go into the main drain stack as everyone seems to have agreed on.

Oh, and I should also add that I was originally wanted to put the sink further away because that was the best location for it in terms of convenience. However, if it needs to be <5' from the vent, then I think I will just relocate it to be closer to everything.

But thank you again so much, I learned a lot reading all your responses (took me a while ). Happy New Year, everyone!

 

[Ginsa]

Maryland code is shown as being the IPC according to this list...

https://www.plumbingforums.com/threads/plumbing-code-by-state.5654/

This is not entirely true but close enough.

I don't believe this requirement, "the standpipe P-trap must be at least 6" above the floor but no more than 18" above the floor.", is included in the IPC.

Regarding the statement/question, "I was just reading something that said if you tie something else in to the horizontal drain for a washing machine that the horizontal drain needs to be a minimum of 3" diameter." I believe this would be the case when using one of the newer High Volume washing machines that exceed the listed DFU's. Whether the code mentions it or not!

Here's an interesting requirement in the 2018 IPC...

View attachment 19446
So now, I believe, we have the option to move the existing standpipe closer to the laundry sink to meet the above requirements.
Whaddaya think?

EDIT:
Definition of laundry tray: a fixed tub (as of slate, earthenware, soapstone, enameled iron, or porcelain) with running water and drainpipe for washing clothes and other household linens
— called also set tub

Oh, sorry, Diehard, I didn't see your new post when posting my reply above.

This 802.4.3.1 Part is really interesting! Does that mean I can connect the drain from the laundry sink to the standpipe as long as the standpipe is >30" above the trap (which I think it is) and higher than the sink?

 

[Diehard]

First off, I'd like to say with regard to your sink location, it can be further away if you go with one of the options showing the separate drain line and separate vent reconnecting to the existing piping.
It's the distance from your trap to the dedicated vent connection that is limited.
I'd like to hear frodo's take on that code requirement.

 

[Zanne]

Ginsa, as Diehard said, you can have the laundry sink farther away if you have an auxiliary vent that goes up and then merges with the main vent so long as the auxiliary vent starts within the parameters. Out of curiosity, are you able to provide a picture or sketch of the general layout of the room? It might help to visualize and see how things fit together.

I would still recommend bringing the P-trap for the standpipe up a bit, which allows it to be taller in case you ever want to add a pedestal under your machines.

Diehard, does the code have any figures to show how the laundry basin would tie in to the standpipe? Are we talking about it tying in at the point where the hose goes in? Sort of like a dishwasher tying in to the kitchen sink's plumbing? (in which case the sink would not need a trap & would share a vent with the standpipe?)

As an aside, is this configuration to code?

 

[Diehard]

Diehard, does the code have any figures to show how the laundry basin would tie in to the standpipe? Are we talking about it tying in at the point where the hose goes in? Sort of like a dishwasher tying in to the kitchen sink's plumbing? (in which case the sink would not need a trap & would share a vent with the standpipe?)

As an aside, is this configuration to code?
View attachment 19456

All I saw was that statement I posted. I too had that question in my mind. It seems to me they're talking along the lines of what you show in your drawing. I have never seen anything like that, in any of the codes before.

 

[frodo]

This is a new addition to the code, OR, I have simply missed it
suds and water will back up in the sink,
This is a good alternative for an addition in a laundry room

I will bet a day old bologna sammich we will see laundry tubs 5' and 8' from the washer
lol..

The kicker here, is the height of the tee for the washer ptrap
this is what is going to be The PITA
in order for the stand pipe to be low, the tee for the trap needs to be low
the higher the tee, the higher the stand pipe above the washer is going to be.
if you will notice on most washers, the hose reaches to the top of the washer
soooooo...replacing the hose is going to common place if the tee/trap is not sitting on the floor


View attachment 19457

 

[Diehard]

Well there you go @Ginsa!
No trap for the laundry sink and just connect it directly to your existing standpipe, but must maintain a maximum of 30", as stated. So to position the sink further away from the washing machine you would have to move the stand pipe.
Plenty of options.

 

[Zanne]

Frodo to the rescue!

 

[Diehard]

Frodo to the rescue!