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Author:
gbonawitz (PA)
Hi. I’m converting a single vanity to a double, and need some help a) validating that two design options could theoretically work, and b) choosing which solution is best.
Background:
- stack/drain is 3”, and existing trap output pipework is 1 ½”.
- I can run pipes along the floor because of the height of the new vanity (and the fact that you can’t see underneath it because of the vanity’s design).
- picture: [i766.photobucket.com]
Solution A:
Splice (probably wrong term for plumbing, but I’m used to it from electrical work ? ) the output from the [new] left sink’s trap into the main waste/vent pipe, downstream from the existing/right sink’s output. In the green circle in the picture I’d replace a section of the 3” drain with a 3x3x1.5 wye + 45 degree bend, run that along the wall to the section circled in blue which is a 45 deg horizontal bend going into a 90 degree horizontal-to-vertical bend [and then up to the output of the trap]. My immediate question on this solution is if the proposed design in the blue circle is OK?
Solution B:
Cut out the sanitary tee (3x3x1.5) circled in red, and replace with a double sanitary tee (3”). The new double sanitary tee would hook back into the existing piping on the right, and then I’d ~ mirror that piping on the left side going out to where the left sink will be. My main ~ concern here is that I can’t find a 3x3x1.5x1.5 PVC double sanitary tee (or double fixture tee), so I’d have to put in some reducers (in reverse) to go from 1.5” to 3”.
Could either of these work? Is there an even better option out there? Any recommendations on which solution to go with?
Thanks in advance!
Edited 3 times.
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Author:
packy (MA)
solution B is what you want.
forget solution A as it is not a legal set-up..
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Author:
m & m (MD)
You should have no problem finding a 3X3X2X2 double tee and then just bush down to 1 1/2".
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Author:
gbonawitz (PA)
Thanks Packy for your response.
Since I likely don't have any wiggle room (vertically on the stack nor horizontally on that exiting 3"drain on the floor) I'm guessing that I'll have to use slip fits at two places once I cut out the existing piping:
1) above the future double sanitary tee (replacing the existing single sanitary tee) on the stack
2) along the existing piece of 3" drain on the floor (I just don't think there's enough length between the bottom of the existing sanitary tee and the 90 right below it to only splice in the new double sanitary tee)
Assuming there is no other option (which I wish there was b/c the ~ buldge from the slip fit on the stack will likely force me to ~ thin out the drywall a little that'll cover it), is there any preference to using a PVC coupler piece versus one of the rubber couplers? I suppose with PVC and cementing I get a better seal.
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Author:
North Carolina Plumber (NC)
I'm 99% sure that I could get a double tee on that 3" pipe without any slip fittings or no hub bands. Even if you must use them they won't bulge out any further than the tee that's in there now will. The tee that's there now is a mite low, so all you'll need is one coupling and a back to back fixture fitting, and of course two 1 1/2" 90's to stub out of the wall with.
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Author:
gbonawitz (PA)
North Carolina Plumber...
I'm trying to picture what you're saying in my head..
1) Cut the existing sanitary tee out with the bottom cut flush with the bottom of the tee
2) If I were to then right there drop on the double sanitary tee, it would sit lower than the existing tee (on whatever short length of 3" about the 90 remains)...which would require lowering that arm coming into it..right? (I guess maybe that's perhaps do-able with some 45s and short lengths of 1 1/2)
Wouldn't there still be a gap above the original tee that I cut out that I have to make up somehow [ultimately with a slip fitting of some sort]? (I do see your point now that any fitting would not be any thicker than the existing tee :-p )
(The gap b/t the top of the 90 and the bottom of the existing tee is 2" while the smallest coupler that I have is 3 1/4... [i766.photobucket.com])
Edited 4 times.
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Author:
sum (FL)
NOT A PLUMBER.
If you cut the existing sanitary tee out at it's bottom, there are various way to get a new double sanitary tee at the original height. For example, you can put a coupling over the cut end of the pipe, then instead of using a regular double sanitary tee as planned, you use one where the bottom is a street or spigot connection into the coupling. That should get you close to where the original branch height was. There are other ways.
From above you can cut out more of the PVC pipe to give yourself some wiggle room. Once you have the sanitary tee properly measured and positioned, you can cut a piece of 3" PVC pipe and glue to the top of the tee. The joint at the bottom would be solvent weld PVC. The joint at the top connecting to the existing 3" PVC could be a shielded rubber coupling, or a 3" PVC repair coupling.
The shielded rubber coupling is easier to install all you have to do is to slide it on and fold it back and you can concentrate on getting the bottom connection properly seated and pointing in the right direction.
The repair coupling looks the same as a normal coupling but does not have a ridge in the middle, so you could slide it completely over one pipe, put the whole thing into position, then slide it over the middle. However it is more difficult as you probably need to apply PVC glue onto both upper and lower joints at the same time and you only have a few seconds to get both the top and bottom right.
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Author:
North Carolina Plumber (NC)
By code you can not lower the arms to meet the tee, that creates a partial S-trap and is a code violation. The lavatory arms must run horizontally into the tee.
I had in mind to raise the tee and drill new holes for the right hand lavatory, as it appears too low right now. I may not have expressed my thoughts correctly.
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Author:
hj (AZ)
quote; so I’d have to put in some reducers (in reverse) to go from 1.5” to 3”.
I don't know what you mean by "in reverse", because if they were in reverse they would be "increasers". Bushings into the 3" double fixture fitting would be the easy way to do it.
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Author:
hj (AZ)
A double fixture fitting is the proper one to use, NOT a sanitary cross, even though some inspectors would approve it for a 3" line.
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Author:
hj (AZ)
Cut at the bottom of the existing tee and somewhere above it. Install the double fixture fitting. Its side inlets are higher than your sanitary tee so the branches will still be in the correct place. THEN, install a piece of pipe on top of it to match up with your second cut and couple it together with a slip coupling or "transition" coupling.
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