How to tie in a back-to-back sink to an existing horizontal drain line?

[oldandslow]

Hi Everyone,
Thanks for a great forum!

I want to add a utility sink in the basement backing to an existing bathroom sink, but I'm not sure how to connect the drain pipes. I searched the forum and found great examples using a "double fixture fitting", but my drain pipe runs sideways, not down (see picture), so I can't figure out how to tie in a second drain on the other side of the wall. In the picture I believe the drain pipe exits horizontally to the right, and the vent pipe is immediately to the left via a 90 degree sweep.

Is it acceptable to splice in something like this on it's side, downstream of the existing sink drain? "Charlotte Pipe 2-IN ABS TEE WYE", Model #ABS 00501 0800.

https://www.lowes.com/pd/Charlotte-...3b44Q9qmMf22Ngmxg-hoCr-EQAvD_BwE&gclsrc=aw.ds.

....Or does that risk waste backing up from the new drain to the original?

Thanks in advance for your help!
Rob

 

[WorthFlorida]

https://www.co.lincoln.or.us/sites/..._-_helpful_hints_residential_construction.pdf

 

[Sponsor]

 

[oldandslow]

https://www.co.lincoln.or.us/sites/..._-_helpful_hints_residential_construction.pdf

Hi WorthFlorida - Thanks for the quick reply, although for some reason I can only see it in the email notification, and not in the forum .

Here's what was in the email:
"That is the correct type of tee to use for a horizontal connection. However, this picture of the bathroom sink seems to show a sani-tee that is only allowed to be used for vertical connections."

Sadly I'm not surprised. The previous owner made a lot of "not-to-code" changes to the house. How would you recommend correcting the existing sink AND adding the new one?

Thanks again!

 

[wwhitney]

What plumbing code are you subject to in Kansas City, MO? up.codes says Missouri has no state-wide plumbing code, and it varies by locality.

And what size are those pipes on the left and right? If you are under the IPC, then a 1-1/2" horizontal drain can carry a lavatory and a utility sink. But the UPC would require a 2" drain.

If you confirm that the pipe on the left is a dry vent, and on the right a drain, then your current configuration is not proper, as WorthFlorida mentioned. But it can certainly be rearranged to be compliant for a lavatory. And if you're under the IPC, or under the UPC and the drain is 2", you can add in the laundry sink that shares the same vent.

Cheers, Wayne

 

[oldandslow]

Hi Wayne, thanks for the information!
1) Code - I'm still researching, but it appears that City of Kansas City, MO adheres to UPC
2) I'll measure the pipe when I open the other side of the wall (this is an old pic, I previously repaired the wallboard), but *guessing* from the hole in the stud, this is 2" ABS
3) How can I tell if the pipe is a "dry vent" (novice here!) I assume that means it only allows gases to escape, and is not a water drain from anything above. I plan to open the wall, have someone run water in the one bathroom above it, and listen. Judging by it's location vs the sink above, I suspect it's dry.

Assuming it's dry, I still need to understand what fitting I should use to (a) fix the incorrectly plumbed existing sink, (b) add the new sink drain, and (c) connect it to the dry vent.

Thanks again for the help (and patience!)
Rob

 

[WorthFlorida]

Sorry for the delay, I had deleted my comments and it's why you only has a partial message.

A bathroom sink usually is a 1.25" trap, utility and kitchen sinks are 1.5" traps. It does look like a 2" pipe. The slip nut to the drain at the wall is the same, the washer used on the slip nut are in two sizes to accommodate either trap arm.

Connections to horizontal drain lines should be made with wye (Y) fittings. It is a waste-fitting tee in which the side inlet pipe enters at a 45° angle. A standard wye is a Y-shaped fitting which allows one pipe to be joined to another at a 45° angle. The 45 elbow should be a street elbow that is one end fits inside the the collar of the wye. Just makes it easier. All are available in ABS pipe. If you cannot get everything in ABS, PVC can be used and be sure to get PVC to ABS adhesive,. While you are at it add a cleanout on the horizontal run.

Not sure if there is a proper vent but it wouldn't hurt to add an AAV. One can handle both traps and it needs to be installed after the traps somewhere along the horizontal drain. Google AAV and you'll find dozens of different configurations. If possible see how the horizontal drain is connected to the main stack. A picture if possible.

.

.

https://www.lowes.com/pd/Charlotte-...hedule-40-Spigot-Trap-Adapter-Fitting/3339768

 

[wwhitney]

For the UPC, the utility sink needs a 2" drain, and you will need to vent each (horizontal) trap arm separately. To vent the trap arm while staying horizontal with the drain, you use a combo with the straight through path horizontal, and the side path facing up. After the two combos, you can combine the drains together on the horizontal, using a wye and a (possibly street) 45. The vents have to rise separately to 6" above both sink flood rims; then you can combine the vents with, e.g. a wye and a 45.

Cheers, Wayne

 

[oldandslow]

Thanks WorthFlorida, Wayne! This gives me a lot to work with. My next step is to fully open the well, confirm the vent stack is dry, take pictures, and draw a design of what I *understand* you're telling me...then you can tell me where I need to correct it!

Might be a while - this project is in the planning stage and I have to finish another (non plumbing) project first.

Thanks again!
Rob

 

[oldandslow]

OK, here are the pictures of the existing plumbing (Pics 1A and 1B), and what I hope to accomplish (Pics 2 and 3). Here's my best guess at how it all goes together - appreciate all corrections and suggestions!!

Pictures 1A and 1B: Here's what's currently installed (or my best guesses based on labels and UPC codes)

Fittings, Clockwise from top left:
All fittings and pipes are 1-1/2" (except for large drain stack on left)

A. Location: Top Left
Transition: Turns a corner, horizontal to horizontal. Vent
NIBCO 5807 Series ABS DWV Pipe Fitting, 90 Degree Elbow, 1-1/2" Hub

B1. Location: Top Right
Transition: From horizontal vent pipe on left down to vertical vent pipe to the right
NIBCO 5807 Series ABS DWV Pipe Fitting, 90 Degree Elbow, 1-1/2" Hub

C1. Location: Bottom right, immediately right of sink fitting
Transition: From vertical vent left into horizontal drain pipe
Note: connects directly to San Tee (labeled "D")
NIBCO INC. 455215 1-1/2 In. Abs Dwv 90 Degree Spigot X Hub Street Elbow

D1. Location: Bottom right, immediately left of Street Elbow "C"
Transition: From bathroom sink on opposite side of wall into horizontal 1-1/2" drain pipe, draining to the left
Transition: From vertical vent pipe on right, by way of Street Elbow "C"
NIBCO 1-1/2-in Dia ABS Sanitary Tee Fitting

E. Location: Bottom Left
Transition: Turns a corner, horizontal to horizontal. Drain
NIBCO 5807 Series ABS DWV Pipe Fitting, 90 Degree Elbow, 1-1/2" Hub


Pictures 2 & 3: Desired result - Add the utility sink approximately 23" to the right of the existing sink drain / San Tee
Please suggest corrections!

B2. San Tee replaces elbow - turning up to the left, and connecting to existing vent, below, and new pipe "F" to the right
NIBCO 1-1/2-in Dia ABS Sanitary Tee Fitting

F. New 1-1/2" pipe connecting existing vent to new vent

G. New 90 degree elbow transitioning from new horizontal vent "F" to new vertical vent "H"
IBCO 5807 Series ABS DWV Pipe Fitting, 90 Degree Elbow, 1-1/2" Hub

H. New 1-1/2" vertical vent pipe

I. New Street Elbow
To connect new vertical vent pipe "H" to new fitting, "J", for the new Utility sink

J. new "Wye+45" or "Combination y-1/8 bend"? to connect the:
New vertical vent stack ("H") and elbow ("I") to the new utility sink and the new drain pipe extension ("K)

K. New 1-1/2" horizontal drain pipe, connecting the new fitting ("J") for the utility sink to the old drain pipe via the replacement fitting, "C2"

C2. Replace existing Street Elbow with a new "Wye+45" or "Combination y-1/8 bend"? to connect the:

• Existing drain pipe on the left
• Existing vent stack above
• New drain pipe "K" to the right

D2. Replace San Tee (D1) with a new "Wye+45" or "Combination y-1/8 bend"?
To fix the connection to the existing sink

 

[wwhitney]

All fittings and pipes are 1-1/2" (except for large drain stack on left)

Pictures 2 & 3: Desired result - Add the utility sink approximately 23" to the right of the existing sink drain / San Tee

OK, two important points that are not reflected in your proposed layout:

- Under the UPC, the laundry sink needs a 2" drain (Table 702.1, footnote 2)
- The lavatory vent take-off is not currently correct, so this is the time to fix it.

So you're going to have to run a 2" drain around the corner to your 3" stack, which means adding a 3" x 2" san-tee or combo to the stack. But you can keep the 1-1/2" horizontal vent run and use it for both the lavatory and the laundry sink (by extending it).

Now, to determine whether to add a separate 2" drain below your 1-1/2" drain, or to simply replace the 1-1/2" drain with a 2" drain for both fixtures, you need some information on trap heights. Laundry sinks are often deeper than lavatories, so the existing drain height may be too high. That would call for a new, lower 2" drain.

That means the first step is to hold up your p-trap under the laundry sink, and look at what range of heights above the floor would work for the trap arm to enter the wall. Also, determine the current height of the lavatory drain above the floor (on the side in the pictures), and then check under the lavatory to see if the p-trap can be moved up or down (but probably not down), and by how much.

With that info, we can advise you on how to run the plumbing for the laundry sink and fix the lavatory venting.

Cheers, Wayne

 

[WorthFlorida]

This is a fairly simple to do, as Wayne suggest a 2" drain pipe low enough to handle both traps. From the picture it looks like the san-tee at the stack is 3x2x3. A 2" to 1.5" reducer might have been used, if true, there is a tool you can buy to ream out the 1.5" pipe. The three 3" stack will be the hassle part of the job. You might have to go past the 45 elbow to get things to fit together. google "socket saver" or "pvc reamer". A closer look at the pics the stack has a 45 at the floor and to cut out the 3" tees there is no length of pipe to cut out just the tees. 3" reamers are sold.

This work looks like it was done by a plumber or someone that was very handy. The copper water lines have the old way of making hammer arrestors. These eventually fill with water and makes then useless. Replace them with hammer arrestors by Oatley or Sioux Chief brands. A hacker wouldn't bother with the extra cost for arrestors. Another is the horizontal drain pipe. 1.5" abs must be flexible enough to get the length of pipe through the the studs. The length is longer than the spacing of the studs. 2" might not be flexible enough. To rerun with 2" abs you may need to use two short pieces with a coupler.

 

[oldandslow]

Thanks Wayne, WorthFlorida – great info! Let me see if I understand – responses and questions in blue

Wayne’s comments:

OK, two important points that are not reflected in your proposed layout:

- Under the UPC, the laundry sink needs a 2" drain (Table 702.1, footnote 2)
Rob: Understood – I’m leaning towards replacing the 1.5” drain with a single 2” drain for both.

- The lavatory vent take-off is not currently correct, so this is the time to fix it.
Rob: It’s currently a San-Tee, which I understand is incorrect. Should it be a “Combo Wye” (long sweep?) or a “Wye+45 degree bend” –Is one better?

So you're going to have to run a 2" drain around the corner to your 3" stack, which means adding a 3" x 2" san-tee or combo to the stack. But you can keep the 1-1/2" horizontal vent run and use it for both the lavatory and the laundry sink (by extending it).

Now, to determine whether to add a separate 2" drain below your 1-1/2" drain, or to simply replace the 1-1/2" drain with a 2" drain for both fixtures, you need some information on trap heights. Laundry sinks are often deeper than lavatories, so the existing drain height may be too high. That would call for a new, lower 2" drain.

That means the first step is to hold up your p-trap under the laundry sink, and look at what range of heights above the floor would work for the trap arm to enter the wall. Also, determine the current height of the lavatory drain above the floor (on the side in the pictures), and then check under the lavatory to see if the p-trap can be moved up or down (but probably not down), and by how much.
Rob: The bottom of the lavatory sink drain is 27” off the ground. 20” for the utility sink. I’ve included a mock up picture of the utility p-trap – I think it’s too low to run a 2” drain above the existing 1.5” drain, so it probably makes more sense to just replace the 1.5” drain with a 2” for both sinks – does that make sense?

With that info, we can advise you on how to run the plumbing for the laundry sink and fix the lavatory venting.

Cheers, Wayne


WorthFlorida’s comments:

This is a fairly simple to do, as Wayne suggest a 2" drain pipe low enough to handle both traps.
Rob: Yes, I think replacing the 1.5” drain with a single 2” drain will be cleaner, easier.

From the picture it looks like the san-tee at the stack is 3x2x3.
Rob: Yes, I checked the UPC code and that’s exactly what it is: UPC 039923204240
NIBCO 5811 Series ABS DWV Sanitary Pipe Fitting, Tee, 3" x 2" x 3" Hub

A 2" to 1.5" reducer might have been used, if true, there is a tool you can buy to ream out the 1.5" pipe. The three 3" stack will be the hassle part of the job. You might have to go past the 45 elbow to get things to fit together. google "socket saver" or "pvc reamer". A closer look at the pics the stack has a 45 at the floor and to cut out the 3" tees there is no length of pipe to cut out just the tees. 3" reamers are sold.
Rob: OK, not sure I’m following all this. I think what you’re saying is I can cut off the 1.5” drain pipe and ream out that end of the 3x2x3 san-tee so it fits a new 2” pipe – is that correct? If I do that, do I still have to make changes to the 3” stack? I think I can handle the new drain and vent pipes, but I’m reluctant to cut into a main stack on my first DWV adventure!

This work looks like it was done by a plumber or someone that was very handy.
Rob: Agreed, it doesn’t look like a “homeowner’s special” But I’m curious – why would a plumber have used 1.5” drain pipe (maybe it’s OK for a single sink?) and the san-tee on the lavatory (I didn’t think that was ever OK)

The copper water lines have the old way of making hammer arrestors. These eventually fill with water and makes then useless. Replace them with hammer arrestors by Oatley or Sioux Chief brands. A hacker wouldn't bother with the extra cost for arrestors.
Rob: Good suggestion, thanks! – I have more experience with water lines vs DWV, so I can replace the hammer arrestors while I’m at it.

Another is the horizontal drain pipe. 1.5" abs must be flexible enough to get the length of pipe through the the studs. The length is longer than the spacing of the studs. 2" might not be flexible enough. To rerun with 2" abs you may need to use two short pieces with a coupler.
Rob: Thanks I didn’t think of that! But I’d have probably figured it out as soon as I tried to fit the new ~5’ section of 2” drain pipe between the studs! ☹ I can deal with couplers

WorthFlorida,

Rob: Once again, I really appreciate all the patience and detailed guidance!

 

[wwhitney]

Rob: The bottom of the lavatory sink drain is 27” off the ground. 20” for the utility sink.

I don't follow these numbers, they don't seem to be in accordance with your mockup. But the mockup photo shows enough info on the relative heights. The existing drain line isn't too high for your utility sink, assuming the existing line has sufficient slope.

Rob: It’s currently a San-Tee, which I understand is incorrect. Should it be a “Combo Wye” (long sweep?) or a “Wye+45 degree bend” –Is one better?

So if you want to avoid a short segment of parallel horizontal drains, you need to raise up the lavatory p-trap inside the lavatory cabinet so the lav drain is above your horizontal 2" laundry drain. Standard would be to put a vertical combo 2x2x1-1/2 in the 2" laundry drain, with a street 1-1/2 san-tee on top of that, the side inlet being for the lav drain. If that ends up higher than you can get your lavatory p-trap, you could use a 2x2x1-1/2" wye, with the straight path horizontal, and put a street 1-1/2 san-tee in the side branch, where the san-tee is rotated 45 degrees from vertical. Either way the top of the san-tee is your vent (although in the latter case you'd need a 45 or street 45 on top to get vertical).

The alternative would be to have your 2" laundry drain outside the stud wall until it joins the lav drain. That way you wouldn't have to raise the lavatory p-trap. From the p-trap, you'd use a 1-1/2" long turn 90 to turn horizontal through the studs, then you'd use an upright 1-1/2" combo for the vent take-off, then you'd use a flat 2x1-1/2x2 wye to bring in the laundry drain from outside the wall (likely with a 2" street 45 on the side inlet for the parallel laundry drain).

Rob: OK, not sure I’m following all this. I think what you’re saying is I can cut off the 1.5” drain pipe and ream out that end of the 3x2x3 san-tee so it fits a new 2” pipe – is that correct? If I do that, do I still have to make changes to the 3” stack? I think I can handle the new drain and vent pipes, but I’m reluctant to cut into a main stack on my first DWV adventure!

The 3x3x2 san-tee that's there is exactly what you want, and by itself it would accept a 2" pipe on the side. But the current pipe going in is a 1-1/2" pipe, and the installer used a 2" x 1-1/2" bushing to connect the two (a bushing is basically a ring of ABS to make up the difference). [You're lucky the installer didn't use a 3x3x1-1/2 san-tee, then you'd definitely have to cut into the stack.]

So the question is how to remove the bushing and pipe and leave the san-tee reusable. For the more typical case of, say, a 1-1/2" pipe going into the hub of a 1-1/2" fitting, there are the tools WorthFlorida mentioned that let you ream out the hub. The tools have a cutter whose outer diameter is the outer diameter of the pipe, and a guide disk whose diameter is the inner diameter of the pipe.

But what you need is a cutter whose outer diameter is the OD of 2" pipe plus a guide disk sized to the ID of 1-1/2" pipe. That way you could ream out both the 1-1/2" pipe and the 2" x 1-1/2" bushing, if the cutter has enough blade length to cut all of that at once. ABS is somewhat hard to cut and generates more heat, so it might be hard to cut it all at once, and you'd have to go very slowly to keep things from overheating.

With those caveats, if you got a 2" tool with a removeable disk, as well as the 1-1/2" tool, you could put the 1-1/2" disk on the 2" tool and maybe ream out both the pipe and the bushing.

Cheers, Wayne

 

[Jeff H Young]

Santee installed wrong 3 x3x2 in picture for the vent (flip 180 degree). Your 3 inch drain line becomes a vent where the santee was installed wrong , verify that no drains connect to this vent above . My guess is vent will require re- route or the ever loved aav that gets put on every job nowdays Yes easy job but looks like most of it was done wrong to begin with

 

[WorthFlorida]

I did notice that the vent santee was upside down but the think I believe is this is a wet vent and when a toilet above is flushed you don't want anything hitting the vent pipe. It's working ok as is.

My take on this is leave the 1.5" drain line alone and just fix the bathroom sink tee. Redoing the 3' stack is not for the faint hearted. A bath sink may use no more than a gallon a minute. It's been working fine for years and it might have passed inspection since there must be a toilet in that bathroom and its drain is under the concrete floor. That it not a typical diy'er doing so it's more evidence that this bathroom was installed when the house was built.

For the utility sink, use a pump. Build an air gap drain just like for a washing machine and tee into the existing 1.5" or a direct connection with a check valve. It will need a vent but directly to the outside. Since this sink is nothing more gray water, laundry, paint brushes, etc., the vent pipe can go up to the floor joist and the side of the house above the foundation wall. It's probably will not be used every day and then only limited use. There are no sewer gasses with this.

From liberty pump manual. Do not connect it to the house vent pipe. It does mention that an AAV can be used.

VENT: Provision is made for a vent stack to allow extra volume for high suds conditions, and to allow proper drainage of the fixture. HAND TIGHTEN ONLY. DO NOT CAP-OFF VENT, venting methods (ONE-WAY QUICK-VENTS) must comply with local and national codes One way quick vents should not be threaded into this product directly. Follow manufactures installation instructions. The vent pipe should have a union to facilitate removal if required and be connected to the building or house vent.

With this approach and it works, great, and should the home ever need to be sold and an inspector noticed it, just cap off the drain and remove the utility sink.

https://www.pumpproducts.com/libert...7bPEDqHKdzGmy9CIYm9PGZA9i_0-rYjQaAkxBEALw_wcB

 

[wwhitney]

Santee installed wrong 3 x3x2 in picture for the vent (flip 180 degree).

This has come up before, but air doesn't care which way the san-tee is oriented, it will works either way. And nobody has provided any code language that requires one orientation or the other. Inspectors in some areas may be in the habit of calling it a violation, but I'd like to see what code reference they provide; I think it's just habit and not supported by the code or by physics.

Cheers, Wayne

 

[Jeff H Young]

This has come up before, but air doesn't care which way the san-tee is oriented, it will works either way. And nobody has provided any code language that requires one orientation or the other. Inspectors in some areas may be in the habit of calling it a violation, but I'd like to see what code reference they provide; I think it's just habit and not supported by the code or by physics.

Cheers, Wayne

Inever confirmed whether it was legal nor installed one that way. It could be legal I don't think it wouldn't work . definatly looks like hack work or inexperience , it would get a journeyman run off a job! If a guy inadvertently plumbed a santee that way he would get ribbed about it . if it was repeatedly and guy was new he'd be down the road. maybe its a regional thing? but never looks good here That stack almost surely going upstairs and picking up other drains that probably works fine too . wet venting floor to floor but just guessing

 

[Plumber01]

This has come up before, but air doesn't care which way the san-tee is oriented, it will works either way. And nobody has provided any code language that requires one orientation or the other. Inspectors in some areas may be in the habit of calling it a violation, but I'd like to see what code reference they provide; I think it's just habit and not supported by the code or by physics.

Cheers, Wayne

UPC 905.1
"All vent and branch vent pipes shall be free from drops or sags, and each such vent shall be level or shall be so graded and CONNECTED AS TO DRIP BACK BY GRAVITY TO THE DRAINAGE PIPE IT SERVES."

 

[Jeff H Young]

Not the worst thing you could do in plumbing and probably makes no difference like Wayne says but would get A first year apprentice yelled at and called some names I wont say now but asking you to take a drug test might happen , or to at least share whatever your on. at least in my area

 

[wwhitney]

UPC 905.1
"All vent and branch vent pipes shall be free from drops or sags, and each such vent shall be level or shall be so graded and CONNECTED AS TO DRIP BACK BY GRAVITY TO THE DRAINAGE PIPE IT SERVES."

I'm familiar with that language. It certainly tells you that the vent pipe needs to be level or slope away from the sanitary tee, rather than towards the sanitary tee. And since the sanitary tee normally has pipes sloping towards it, I've often wondered if it's molded as an 89 degree bend instead of a 90 degree bend. In which case it would be easier to get the correct slope on the vent if the sanitary tee is upside down.

But I don't see that language as requiring that the tee be upside down. A 2" sanitary tee has maybe 1-5/16" of run within the side inlet, I don't see that as significant in this context.

And the IPC doesn't use that language, it requires the vent to slope to a drain, not necessarily the drain served by the vent.

Cheers, Wayne