Single to Double Sink - Vent to Right

[Scott Jacobs]

New to forum and so far have learned so much. I know there are a lot of posts on single to double sinks but a lot of them have the vent near or in the center. I did find one that was helpful which I am trying to imitate. But I have a further distance to my vent/drain. This is the thread:

https://terrylove.com/forums/index.php?threads/single-sink-vanity-conversion-to-double-sink.69320/

My existing drain is 1.25 ABS and is about 60" from the 3" ABS vent/drain (highlighted red in picture below). I know that line is too small, but was hoping to use it (if this is a bad idea, let me know and I'll upsize it). I think I know what I'm going to hear.

I'm hoping to use 1.5" for the new stuff. The existing line is a bit low (17" where the old sink was but due to slope it will be ~ 16" where the left sink will be). So I was going to use some 45 deg couplers to get it a bit higher to the left sink. I'm opting to extend the existing line but can switch this if needed.

Thanks for the help!

 

[Scott Jacobs]

I have an option 2 based on this picture from Terry:

Below is my version based on my layout. If this is better than the first one, let me know if 1.5" will work.

 

[Sponsor]

 

[Aaroninnh]

1.5" should work fine to handle 2 lavatories, but we should wait for the pros to weigh in. That said, you will find many go with 2".

I don't like double santees, they can be really hard to snake. You push the snake in one sink and the snake just pops out the other sink.

Here is a quick and dirty (and ugly) drawing for what I would suggest.

I am not a pro.

 

[Scott Jacobs]

Thanks for the input Aaroninnh. I drew up this 3rd option. Let me know what you think. The only reason I like option #2 is there is a little less cutting. Not that I mind drilling the holes, It's just I am worried about too many holes in the studs. That being said, this is not a load bearing wall so it probably doesn't matter much.

 

[Aaroninnh]

Wet walls are often 2x6 for that reason, so you dont end up boring out 80% of the stud...load bearing or not

 

[wwhitney]

Option 3 is good, it's actually the same number of holes as Option 2.

If you are under the IPC (which I think most? of PA is), then the 2" segment could 1-1/2" (IPC horizontal 1-1/2" good for 3 DFUs), which would be better for stud boring. If you go with 2" pipe, you'll certainly need stud shoes for 2-1/2" holes in 2x4 studs (although stud shoes are a good idea, regardless).

The upper right vent san-tee would conventionally be turned up side down from the orientation shown.

Cheers, Wayne

 

[Scott Jacobs]

thanks for the input Wayne. Looks like Option #3 it is then.

Quick questions:

Now that I have 1-1.2 verticals for each sink drain I need to use a tee. Do I use a short tee or a long/sweeping tee for those? I'm worried the sweeping tees will impact my drywall a bit due to the sweep.

Also, I see that you're not supposed to glue PVC and ABS. I was told to get a mechanical connection type. this is what I got:

Will this work? I will then just use PVC to install the 1-1/2 to 3" sweeping tees and then use these flex connectors to get splice back into the 3" abs. Sound good?

 

[wwhitney]

Now that I have 1-1.2 verticals for each sink drain I need to use a tee. Do I use a short tee or a long/sweeping tee for those? I'm worried the sweeping tees will impact my drywall a bit due to the sweep.

Your photo with overlaid fitting icons shows the correct minimum sweep choices in all cases. In particular, the lower left has to be a long turn 90 as shown, and the lower middle has to be a combo as shown.

Also, I see that you're not supposed to glue PVC and ABS. I was told to get a mechanical connection type. this is what I got:
Will this work?

For your new connections to the stack, you have two possibilities: If the vertical pipe extending out the top of the picture is something you can temporarily move upward 3" (say it goes into the attic and hits an elbow that you can lift up, or it can slide up a roof boot and back down without damaging the boot), then you have the option to do all the new work in ABS and just use ABS cement to tie into the stack.

If not, then you'll need to use two rubber couplings in order to insert a new stack segment between two fixed cut ends. In which case you can use either plastic for the new work (PVC or ABS). But the couplings you show are not the correct ones, they are for underground use only. For aboveground use, you need a fully shielded coupling, and they only have to be about 2" long. For 3" plastic to 3" plastic, use Fernco 3005-33 or Mission P-300.

1-1/2 to 3" sweeping tees

I'm not sure what fitting you mean by this, it could be a 3x3x1-1/2 san-tee, or a 3x3x1-1/2 combo. The san-tee has less sweep, the combo has more sweep. For the two right hand fittings in your diagram/photo, you just need a san-tee, as you show in your icons.

Cheers, Wayne

 

[Scott Jacobs]

Thanks for the quick response. I saw the shielded versions of the flex couplers, but wasn't sure. I can go swap them out. I didn't see any abs pipe at home depot which is why I went this route. Where do they sell abs pipe? I can go return everything if you think that shielded flex coupling won't work well over time (I'm kind of skeptical myself).

What I'm trying to decide is which type of tee to come out of the wall, where my trap arm will connect. These have to be tees because of the vertical sections of 1-1/2" pipe. I think you are supposed to use the longer sweeping tees for horizontal work, but not sure. The shorter tee will easier to drywall around as it comes straight out compared to the lower one.

 

[Tuttles Revenge]

Most of the country only uses PVC nowdays from what I understand. But the bands you will use to tie into the stack allow you to convert from one to the other. I agree with Option 2 or 3.

You would use the San Tee/short radius tee to stub out. Also that would be the correct Tee to connect to the Stack both as the drain and as the vent as Wayne pointed out above. It allows proper venting of the trap. If you imagine a line at the center of the horizontal run into that tee.. it needs to be half air into the vented vertical while the bottom half needs to carry the liquid waste down.

 

[Aaroninnh]

There is a green transition cement that does a decent job solvent welding PVC to ABS, but I don't think its legal everywhere.

Ive used it and its still holding strong.

https://www.homedepot.com/p/Oatey-16-oz-Green-ABS-to-PVC-Transition-Pipe-Cement-30925/100200776

 

[wwhitney]

What I'm trying to decide is which type of tee to come out of the wall, where my trap arm will connect. These have to be tees because of the vertical sections of 1-1/2" pipe.

To amplify Tuttle, for a vent take-off, such as where the trap arm enters the wall for your layout, you must use the short radius tee (sanitary tee). The long radius tee (combo) doesn't allow the air in high enough in the trap arm and can allow siphoning of the trap.

Cheers, Wayne

 

[Scott Jacobs]

I appreciate all the help from everyone. Install today!