Moving kitchen sink and dishwasher, vent question

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clix

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Our current kitchen remodel plan calls for sliding the kitchen sink 8' to the right, on the same wall where the current sink is located. The vent for the current sink location runs vertical directly behind the sink before turning horizontal and then vertical again after clearing the window over the sink. I have a drop ceiling in the basement below and current drain lines run below the floor joists in the basement.

What I would like to do is tie new sink into the existing drain and be done but I understand that the horizontal length of the trap arm would exceed the maximum length provided in the UPC. I see a couple ways to address this, but not sure which is best and if they all comply with the UPC.
  1. It seems that running running vertical in the wall behind the new sink and then cutting over to tie into the vent at the current sink location is the obvious way to do this but would like to avoid boring through the 2x4 load bearing wall for an 8' stretch (#1 in drawing).
  2. Another option would be to extend the trap arm as far as I can under the floor and then cut vertical so that I'm only boring through a couple load bearing 2x4s. (#2 in drawing).
  3. Curious if running underneath the floor for a span and then turning vertical within the maximum trap length specified and then running horizontal under the floor for a couple feet before turning vertical to tie into the current sink vent location (#3 in drawing). Essentially, this would do all the "work" under the floor so that I would pop through the floor and into the vent without disturbing the load bearing wall. I might need to drill through the middle of one or two floor joist to do this. I'm guessing this won't work because of the horizontal vent below the sink. If this doesn't work as described above, would adding a loop like you would for an island and then running that to the current sink vent location under the floor be an option?
Appreciate any feedback or other suggestions anyone has. Thanks again in advance for the help!

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Cacher_Chick

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The trap arm is the horizontal pipe which leaves the trap, and the vent take-off must come off at that level, not below the trap.

Your options are to install a proper vertical vent at the sink location to the roof or take it up to the ceiling level and then arm over to the existing vent, and box that into a soffit or through the cabinets. If your code allows, an AAV could be used, but that should be considered a last resort.
 

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Thanks for the response. Won't be able to run to the roof or build a soffit. Is a loop not an option here because there's a wall? I assume dropping the trap down below the floor (it would be accessible) isn't an option.

The trap arm is the horizontal pipe which leaves the trap, and the vent take-off must come off at that level, not below the trap.

Your options are to install a proper vertical vent at the sink location to the roof or take it up to the ceiling level and then arm over to the existing vent, and box that into a soffit or through the cabinets. If your code allows, an AAV could be used, but that should be considered a last resort.
 

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Loop vents are only approved for situations where there is no wall, such as in the case of an island sink.

The maximum length of a tailpiece is 24", which even then would be unheard of, because the trap must be above the floor.

The vent must be vertical until it reaches a point no less than 6" above the flood rim of the sink.
 

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Thanks. After looking a bit more behind the drywall I see there is no upward portion after the p-trap until the drain hits the vent, from the p-trap the pvc goes down through the floor, cuts over about 5' and then ties into the stack. This seems to fall within the 60" trap arm length permitted for a 2" trap arm pipe diameter but the point where the vent is tied in (below the floor) is well below the p-trap. Just wondering how this would comply with the requirement that the vent take-off must be above level of the p-trap.

It also appears that my second floor shower is draining is on top of the kitchen sink vent and drain. This is a bit more than an 8' piece of the kitchen sink vent that is under the shower drain. Is this wet vent something that would be UPC compliant today? The house was built in the early 80s and this appears to be the original plumbing.
 

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There are plenty of homes out there that were not plumbed properly. If you are doing a remodel, anything you install will need to meet code and pass an inspection.

Wet venting is not allowed between floors in the U.S.

If it is a double-basin sink plumbed to a 2" horizontal branch, the trap to vent distance cannot exceed 8 feet. This is assuming that the trap arm and branch drain is pitched 1/4" per foot.
Any vertical jog between the trap and vent breaks the vent and is therefore not permitted.

Turning downward after the trap is considered an S-trap, and is not permitted under any code I am aware of.
An S-trap will siphon, and sewer gas will come back into the house.
 

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So, I figured the house was built to code originally and that I hadn't found everything. I thought I had traced everything but after reading your last post, I took out more of the wall under the sink and see that what I thought was the vent for the sink isn't. The sink drain and vent start on the right of the sink, vent runs straight up, the drain side ties into the same stack with the shower in the basement to the left of the sink.

In the current layout, with this newly discovered drain and vent, I've got about 7'-8' from the sink to the vent. About 3' of that will run under a large window, leaving 4'-5'. I think I'm limited to drilling 1-3/8" holes in the load bearing 2x4s over that distance. It doesn't seem that a 1" (or a 1-1/4") pipe is sufficient to meet UPC venting requirements, so I won't be able to run from the p-trap, up to the bottom of the window and straight over to the vent I want to use.

I'm thinking that I may need to run 1-1/2" pipe up the edge of the window into the floor joist space for the second floor and then drill the joists make my 4'-5' run over to the vent I want to tie into. Does that sound like it will work?

I may be able to swing this, as you suggested earlier, through cabinets or above the cabinets. (Given that the vent is on the right side of the sink, there is a better chance that I will have cabinet coverage for most, if not all of the span over to the vent. If I can get into the space above the cabinets, I may have to drill through only one floor joist if the cabinets don't cover the span completely but don't know if that's worth trying to avoid one or two extra holes in the joists.)

Any thoughts as to the best approach here? I know you already suggested the soffit/cabinet route, but not sure if the joist space option is a good idea. I think it will be easier to tie in within the joist space as I think the vent runs right next to a stud.

Thanks again for the assistance!
 

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Double up the studs and drill 2" holes, and then reinforce with stud shoes.
 

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clix

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Double up the studs and drill 2" holes, and then reinforce with stud shoes.
Interesting, will look into that and check building code. I assume you wouldn't have suggested if this wasn't generally fine for load bearing walls but I'll want to make sure no weird rules here.
 

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It is the inspectors call as the issue of steel reinforcement of studs does not come up in the building code. At least is has not yet.
 

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Would this be preferable to drilling a 2" hole through a few 2x10 floor joists overhead? If I did that, I would drill the holes in the middle and would come in a foot or two (or more if advisable) from the load bearing end. Was thinking that would be the least intrusive way to go about it if I have to drill horizontally.

I will see if up and over the cabinets will work as that would involve the fewest holes in load bearing members. May also just scab on a 2x3 wall for running the pipes.
 

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You can do any of these things, remembering that you will need to maintain pitch to drain throughout the vent, and that you are going to need to piecemeal short sections of pipe through the framing and couple them back together.

Another option that is sometimes used if you are willing to lose a little space and build out the window jambs is to build another complete wall to the inside of the existing one. In doing this you can also greatly increase the R-value of that wall through by offsetting the studs and insulating the interior wall. You will also have to consider your cabinetry and rewiring the wall as required.
 
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