Proper slope for sink drain?


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Old 11-16-17, 07:27 AM
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Proper slope for sink drain?

I am installing a new vanity, but because of the way they originally set the plumbing up, I have to run some stupid setup with a pipe under the vanity, then up, then to the p-trap. I just have a question about the proper slopes of the horizontals. Just make them level or slightly towards the main drain?
 
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Old 11-16-17, 08:22 AM
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1/4" per foot I believe, you don't want it level.
I would check back for additional responses, I'm not sure if what you are doing is up to code. Is the pipe going to the right under the floor or is it inside the toekick of a vanity?
Either way I would check back.
 
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Old 11-16-17, 08:27 AM
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It will be under vanity and above the floor. There is a 4" space. Whether it is or is not to code is of no consequence because I'm not tearing up the floor.

That drain in the wall is on the right side of the vanity, they stupidly did not put it at the rear of the vanity with the water supply lines. Right now, the drain is about 18" above the floor, because the original vanity had no drawers on the sides, it was just a cabinet, so they ran the PVC thru the vanity to the center section to the p-trap. My new vanity has drawers so I'm moving the sani-tee in the wall down to the floor to run the drain as I drew.
 
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Old 11-16-17, 08:38 AM
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It sounds like you're fine and I would do the same.
 
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Old 11-16-17, 10:44 AM
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K thanks.......................
 
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Old 11-18-17, 10:24 AM
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Can I still get a good PVC seal if I cut the sealing surface down from 1.5" to 1"? I could use an extra .5" of clearance for the drain under the vanity.
 
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Old 11-18-17, 11:44 AM
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I for one do not understand your question. What is a sealing surface?
In my post above I said I would do the same as you are doing, but actually I would run the drain line in between the drawers or in the wall.
That's harder to do but your idea will work.
Do not reduce any pipe. I would recommend 1-1-2" and that's including a 1-1/2" trap, not 1.25.

If you are talking gluing surface, a typical PVC or ABS fitting only inserts the pipe about 3/4" into the hub. Don't cut the hub down or shorten it, bore a larger hole if necessary.
 
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Old 11-18-17, 02:24 PM
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FYI, the way you have it sketched out is not to code. I'm not telling you that you can't do it, but just that it's not the way it's supposed to be done.

The issue is with the vertical drop before a vent. You might be better adding a sanitary tee after the p-trap, with an AAV on the vertical section. It will help ensure the trap isn't sucked dry and sewer gasses aren't allowed into the house.
 
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Old 11-18-17, 04:01 PM
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Like this...

 
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Old 11-19-17, 08:01 AM
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That's not a problem, I can add that vent. But I don't see how the trap could get siphoned out with a slight downward slope on the horizontal?
 
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Old 11-19-17, 09:07 AM
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You want to keep the slope on the horizontal.
The concern is the vertical drop from the trap down into the vanity bottom deck/toekick. Usually a pipe runs directly to the right in your sketch, not down and then to the right.
Like the guys said, add the AAV and you're set. The mark/line on the AAV should be 6" minimum above the trap arm. Mike's picture is perfect.
 
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Old 11-19-17, 11:02 AM
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So here's my problem and why I asked about the PVC sealing flange surface. I can't go down into the floor anymore, and I need to get this pipe under the vanity, which only has 4" clearance. If I can cut .5" off the sani-tee, and butt it against the floor, I'll have enough room. Believe me I know it's not ideal.
 
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Old 11-19-17, 11:34 AM
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I've been installing kitchen and bath cabinets for over 17 years professionally. I never had a problem running the drain line in between the drawers.
You might want to go that rout. It's going to make your job easier and it will be up to code.
Seeing the horizontal pipe inside the cabinet is not a concern IMO.
 
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Old 11-19-17, 05:16 PM
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Here's the vanity. How could I run it thru that side drawer section?
 
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Old 11-19-17, 05:34 PM
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Can you take an overall pic of where the vanity is going in relation to the stub out? This may result in a better solution...
 
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Old 11-19-17, 07:10 PM
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Yes, that's a tough one. I would consider eliminating one drawer. You can make the drawer a false front or a tip out tray.
 
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Old 11-19-17, 07:20 PM
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With some forethought, those walls could have been furred out (or changed to 2x6) so that the drain could be run straight back into the wall directly behind the vanity... at the proper height, with the proper slope, around the corner to the stack, with a vent up the wall behind the vanity.
 
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Old 11-19-17, 08:44 PM
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Here is the location............
 
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Old 11-19-17, 09:04 PM
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Geez man!!! Cut the wall open and run the pipe behind vanity... come out between the water lines..

Or with that vanity simple cut two drawers and make them 1/2 drawers or take out completely and glue the face of the drawer to front. ( It will be two fake drawers...)
 
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Old 11-19-17, 09:07 PM
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. .
 
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Old 11-20-17, 06:37 AM
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Believe me I thought exactly of what you drew there, but I wasn't sure if you were allowed to notch out studs. The only thing above it is attic so I guess it doesn't matter. I was caught up on the thought "Why didn't they just run the pipe that way to begin with?". **** it maybe I'll just do it.
 
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Old 11-21-17, 04:32 AM
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Can someone please tell me it's OK so I can feel good about it? Haha.
 
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Old 11-21-17, 04:59 AM
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It's 3 feet, and its an interior wall. I doubt the house will collapse. Cover your notches with a Simpson stud shoe.
 
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Old 11-21-17, 06:56 AM
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Perfect! Thanks guys!..........
 
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Old 11-22-17, 01:34 PM
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Found out why they didn't do it. There is another vent in the wall. It's tied in as shown below. Can I tie it to the main vent at a lower position? I could tee it in just under the tee for the sink drain.
 
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Old 11-22-17, 03:48 PM
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That's fine but what does purple line tie into??? You have to be more specific and detailed....
 
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Old 11-22-17, 07:29 PM
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It's a vent for the 1st floor bathroom sink, right below this bathroom.
 
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Old 11-22-17, 08:44 PM
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No you cant do as you show.....
 
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Old 11-22-17, 08:48 PM
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This is all you can do...'
 
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Old 11-22-17, 09:02 PM
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Mike, you are obviously the authority on this... but I wonder if it might be possible to move the vent (the one currently in the floor) to another location... either up the wall behind the vanity... or the opposite direction to a different wall. Then tie the vent back into the stack up in the attic.

Doing that would get rid of the vent obstruction and allow him to run the drain through the wall like you said in #19, 20, wouldn't it?
 
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Old 11-23-17, 12:14 AM
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clearly the purple line is a vent for something else. I may have miss spoke on my drawing in that you cant wet vent. I need to know what the purple line connects too....
 
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Old 11-23-17, 06:43 AM
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Can I ask why I shouldn't do it as I drew? It's a vent for the 1st floor bathroom sink. If I install it how I drew it, no water from the 2nd floor sink could run into the 1st floor sink vent, at least not that I can see.
 
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Old 11-23-17, 09:55 AM
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Slade, the way you drew isnt proper because it is wet venting, and your 1st floor vent needs to be higher than the highest drain. (Like it is now). In post 25, you have it venting into the stack below the 2nd floor drain.
 
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Old 11-23-17, 04:44 PM
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Yeah youll have to do as I show here. And tie the new sink line into the stack below floor level as I show. You cant tie into the purple line at all as it will be a wet vent...
 
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Old 11-24-17, 07:58 AM
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Ah OK I see. What's the problem with 'wet venting' as I've drawn it? Could it cause a problem with the 1st floor sink?
 
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Old 11-30-17, 05:51 AM
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Definitely some ****ty work in my house. I don't think you're supposed to have 3" fittings inside a 2x4 wall because it bows the sheetrock out since the fitting OD is 4".

Another thing I noticed... why is it that kitchen sinks don't have vents like this? Is it because the dishwasher or garbage disposal line acts as a vent?
 
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Old 11-30-17, 06:28 AM
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Kitchen sinks should have vents.

In a pinch, you can route out the back half of the drywall to fit over the hub and lay flat. But you are right, it is better to fur out the wall or use a 2x6 wall if a stack will be in it, as mentioned in post #17.
 
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Old 12-01-17, 07:31 PM
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This is the 2nd time I've coupled this pipe and both times leaking at the same point. Leaking out of the bottom part of the bottom coupler. That bottom pipe is original from the house, 1985. Is there something I can do, some type of sealant or something so I don't have to cut the section out and add 2 new couplers in???
 
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Old 12-01-17, 08:11 PM
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Cut it apart and use a shielded Fernco instead of a glued coupling. I'm trying to figure out why your tee is so high.
 
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Old 12-01-17, 08:17 PM
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The sink is pretty high.

What's the shield for, as opposed to the regular rubber ones?
 
 

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