Island Sink in Basement Question

How high can the tie-in to the drain pipe in the wall be on an Island Sink?

Right now I'm looking at about 25 inches. I have about 14.5 feet to go to hit the main 3" drain pipe in the basement from where the sink will be in the Island. The height of the drain pipe at the sink is dictated by the allowable slope (1/4" per foot) and by the minimum height for the tie-in to the 3" line based on the Wye pipe that will go there. Based on a quick measurement it looks like the lowest I can go at the sink is about 25". Typically the pipe height for a drain is about 17". Is 25" too high or will that work as long as I select the right sink?

I'm wondering if there is a minimum height above the trap? Or, is there a minimum distance below the bottom of the sink the pipe has to be?

As long as the pipe is below the sink and has the proper slope and vent, it will work but there is always the issue of what an inspector will accept.

re5513.

There is a maximum length of the sink tailpiece, but I don't think there is a minimum, except that dictated by the available traps.

island sink

Either you are defining "island sinK" differently than we are used to or we have to see how you are running the pipe. An island sink, typically, is in an "island" and therefore there is no way to run a pipe to it above the floor.

Basement sink.

hj said:

Either you are defining "island sinK" differently than we are used to or we have to see how you are running the pipe. An island sink, typically, is in an "island" and therefore there is no way to run a pipe to it above the floor.

Click to expand...

True. In this context the sink drain is not in an island but located in a 1/2 wall/bar who's end terminates in a wall that hides a storage area in the basement. The drain pipe will connect to the sink through this 1/2 wall. See below. . The 3 inch vertical drain pipe I have to tie into is shown in the left of the photo. The bottom of the end of the measureing tape shows where the 1 1/2 inch drain pipe would come out of the wall.

It sounds like as long as I can hook up a trap to the drain and the pipe I should be OK.

re5513

You need a vent...one of the pros can help you figure out how to run one that will work and pass code (I hope!).

island sink in basement

First of all a 14.5 ft run of 1.5" pipe at .25" per ft equals a slope of less than 4" of fall,and that should solve your rough-in problem,as far as venting you could use an air admittance valve or tie in to existing vent 6" above the flood level rim of the vented fixture.

drain

1. that is too long a run for 1 1/2" pipe.
2. the connection will be with a sanitary tee, not a "Y".
3. you need a vent connection within 5' of the trap, (assuming 2" pipe, 42" for 1 1/2").
4. the maximum height of the drain pipe will be dictated by the type of sink and whether it has a disposer or not.

hj said:

1. that is too long a run for 1 1/2" pipe.
2. the connection will be with a sanitary tee, not a "Y".
3. you need a vent connection within 5' of the trap, (assuming 2" pipe, 42" for 1 1/2").
4. the maximum height of the drain pipe will be dictated by the type of sink and whether it has a disposer or not.

Click to expand...

1. OK, 2" pipe now being used.
2. Copy that. sanitary tee to be used.
3. Using a Studor vent, AAV.
4. I'm planning on using a dual sink (kitchen type) with two 7" deep bowels. I will have a garbage disposer and a dishwasher output feeding into the same drain system.

I reviewed this plan with the inspector and for the most part, all is well. I am still having a bit of trouble designing the actual interface between the 2" drain pipe and the various traps, etc. & vent. Knowing which fitting to put where is not an easy exercise for me. This was made somewhat more difficult by the inspector who insisted I not ask questions that might lead me to designing the drain system on the spot. Evidently, they are allowed to comment on a proposal but cannot provide design information.

So I'm still looking for a little help here from this forum. The inspector did suggest that I tap into the drain stack below the cleanout (instead of above it, as I had planned originally). This would allow me to lower the drain pipe at the sink considerably. That being said, it seems he wants me to turn up the pipe (in the wall) 90 degrees and then he wants to see two drain pipes in the cabinet, one for the sink and one for the dishwasher. This is where I am not clear. I passed one design by him that put the tees for the two drains in the wall with the AAV tying into a pipe that connects to the top of the last tee as shown below:

Sideways view in the wall

=
AAV: |_________
|
|
Sink drain -----------
|
DW Drain ----------|
|
^ |
inside cabiets |____| < 1/2 Wall

So, after I proposed this, the inspector asked me if I could think of a way to not stack up the tees in the wall. I started to suggest alternates and then he decided he was doing too much design work for my project.

He did offer that what I was trying to do was very common. A solved problem and that I should be able to find an example elsewhere. Hence, if any of you have a pointer to a drawing or example of a better way to do this I would be very pleased to see it.

re5513

Venting is not impossible, one just has to be creative.

AAV's are for the lazy...end of story.

Sounds like you might know more than your inspector, hehe.

Use the dishwasher connector on your disposal (and air gap if required) rather than a separate standpipe for the dishmachine.

Dubldare is entitled to his opinions about Studor vents, and while I agree they are not the answer to all venting situtations, they do work and as long as they are installed according to code, they will certainly do the job. I wasn't involved in plumbing when PVC can on the scene, but I can well imagine many of the traditionalist plumbers decried the, "Damn plastic @###" as the lazy way to plumb. For a sink, garbage disposal, and dishwasher in a basement rec room where conventional venting would be very difficult, the Studor is perfect for the job.

While yes, while it is my opinion whether AAV's are for the lazy and whatnot, it is also the law of the land where I practice.

http://www.doli.state.mn.us/pe_aav_order.html

I have shown in my image that providing for venting within the hydraulic gradient is possible, without flat venting. If it is such that no other fixtures exist on this level of the poster's home (where no venting can be found) that is one thing. But perhaps the bigger issue is that these fixtures have not yet existed, and a tie-in near the base of a stack has the proclivity to expose this branch to positive pressure, of which the AAV can do nothing for.

If it were mine, I'd do it the way I describe. I cannot charge someone for less. Those are my drothers. Call me old school, but no one has convinced me that an AAV meets or surpasses a properly installed 'oldskool' vent.


PS: I'm also booked out 5 months, and 2 months behind on some calls. Doing it right doesn't mean you have nothing to do, it just allows some people to find time to wait for it to be done right.

I would remove the cleanout, put a 3x2 san tee in it's place then put a new 3 cleanout above it. This will lower your drain considerably. If you still need to gain some height then instead of standing the tee (2x11/2x11/2) up you can lay it on it's back and vent off the top of it, or use a combination instead. I would show a picture but can't get it to paste.

winslow said:

I would remove the cleanout, put a 3x2 san tee in it's place then put a new 3 cleanout above it. This will lower your drain considerably. If you still need to gain some height then instead of standing the tee (2x11/2x11/2) up you can lay it on it's back and vent off the top of it, or use a combination instead. I would show a picture but can't get it to paste.

Click to expand...

Yes, I think that is a great idea.

So I built up the drain stack and layed out the pipe with the proper grade all the way back to the existing 3" drain. In doing so I made a rather startling discover. That is, the cement floor near the wall of the foundation is anything BUT level. Thus, I will have to raise up my drain pipe about 2" above where it is pictured below.



So I learned today from inspector Daryl that if I have a test tee in the 3" drain I do not need one in my 2" line. Joy of joys. I can take out the one I had put in the 2" stack and that should allow me to lower it enough to keep everything inside of the sink base.

Regarding the use of the Studor vent. I agree that a traditional vent is preferred. In this basement, I have one 2" vent about 25' away from the kitchen in the bath rough-in that I could tie to; however, I don't think they'll let me tee into it. That would mean this single vent would need to support a bathroom sink, shower, and pot, in addition to a kitchen style sink and dishwasher all on the same vent and there would be 25' of horizontal between the basement bathroom and the kitchen area. All the installations I've seen have a separate vent for each drainage area. If tying into the bath vent would pass inspection, I would not have a problem buying the pipe to make it work. But I'm not keen on running a new pipe from the basement to the attic and out the roof. If that is the traditional vent option, the Studor is a reasonable alternative and is legal in CO.

re5513 said:

Regarding the use of the Studor vent. I agree that a traditional vent is preferred. In this basement, I have one 2" vent about 25' away from the kitchen in the bath rough-in that I could tie to; however, I don't think they'll let me tee into it. That would mean this single vent would need to support a bathroom sink, shower, and pot, in addition to a kitchen style sink and dishwasher all on the same vent and there would be 25' of horizontal between the basement bathroom and the kitchen area. All the installations I've seen have a separate vent for each drainage area. If tying into the bath vent would pass inspection, I would not have a problem buying the pipe to make it work. But I'm not keen on running a new pipe from the basement to the attic and out the roof. If that is the traditional vent option, the Studor is a reasonable alternative and is legal in CO.

Click to expand...

A 2" vent is more than likely adequate to vent your entire house, on a fixture unit basis, not an aggregate area basis.

Off the top of my head, UPC allows 24 dfu (drainage fixture units, 1 dfu=7.5 gpm) on a 2" vent up to 40'.

Mn code, which I'm more familiar with, allows 72 dfu on a 2" vent up to 50' developed length. Our dfu ratings are a bit different than UPC, but here's what it would be in Mn:

1 water closet: 6 dfu/minimum 2" vent
1 shower: 2 dfu
1 lav: 1 dfu

9 dfu total existing

add:
1 kitchen sink w/ disposal: 2 dfu
1 domestic dishmachine: 2 dfu (although this is with its own trap, but since the dfu's are greater, lets use it)

add 4 dfu's to the existing 9= 13 dfu's to be vented

Even under the UPC where your water closet would be 3 dfu's, a 2" vent would be plenty sufficient to add the sink into.


If CO is under the ICC codes, they'd probably let you vent the entire house off a studor vent, lol.

PS: Rather than adding a dedicated trap for your dishwasher, why not discharge it into the dishwasher tap on your disposal? That way, your entire sink, disposal and dishwasher would use one trap.

dubldare said:

A 2" vent is more than likely adequate to vent your entire house, on a fixture unit basis, not an aggregate area basis.

Click to expand...

Thanks for the great info.

OK, so my EE brain has ID'd another potential issue, that of grade. I know in CO (and probably elsewhere) we have to maintain a downward grade on both vents and drains. At 1/4"/foot I'd need about 6-6 1/2" of drop in the horizontal span. I'm pretty sure I don't have that much space in my joists but I'll measure it and check. Due to the bath being on the other side of the house there are also many ducts, pipes, and return vents between the kitchen and the bath. I'll take a look at it.

I also thought about putting the dishwasher into the disposer and then just having one 1 1/2" drain under the sink. For some reason that is not the first thought of either regional or a plumber acquaintance. There may have been a code change. In my old house, one drain was how it was done, but this house (2002 construction) and others don't seem to follow that same approach and use two 1 1/2" drains under the sink. I probably should have asked them why not just 1 drain instead of two. "With what you're describing I can tell you what an inspector will expect to see. That is, that the pipe turns up with a 90, and then two san-tees, one for your sink and one for your dishwasher with a vent on top." Is what Daryl at regional described. A big part of my leanings here is to not just build a drain that passes code but to build one that will be a quick sign-off for the inspector. That means building it in a way they are most likely to expect to see it assuming that such an expectation is within reason (which in this case seems true enough).

vents can be level above the flood rim of the fixtures, at least according to the UPC

winslow said:

vents can be level above the flood rim of the fixtures, at least according to the UPC

Click to expand...

Yep. I just checked with regional and the vent pipe can be level. BTW, the distance to the vent in the bathroom is 43' in the horizontal. Thats a long vent.

Thanks again.

winslow said:

vents can be level above the flood rim of the fixtures, at least according to the UPC

Click to expand...

If you have a 2" vent, how far away can the sink drain be.

Also, how would you measure it? From the center of the 2" pipe to the sink? or would it be the distance from the vent to the entrance of the drain pipe?