Rolling island vent in a tight space - can I do this?

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Hudsonmd

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Great forum - thanks for providing it!

I am remodeling a kitchen, and adding an island with a sink. Half the room is over a fairly short crawlspace, the other half is slab. The island straddles the two, with the sink in the middle but mostly over the slab side. I'm in VA, so IPC, so I could use an AAV, but would prefer to use an island vent if I can.

There are two main challenges:
1) the 2x8 joists sit on top of a block wall in the crawl (and are too small to put big holes in, I think) and the vent and drain both need to run perpendicular to the joists (not in the joist space). So I need to go under the joists, but there isn't a ton of space vertically for the 1/4" slope up/down.
2) the sink cabinet is sitting basically on the slab, I'd like to avoid cutting the slab and block wall if I can, but want to get the sink as far on the slab side as possible to allow for walkways around the island.

I'm thinking about adding 45's to both the drain and the vent loop, maybe inside the cabinet. I'm pretty sure this is ok, but would like advice.

Then, ideally, I'd like to add a second 45 to each line below the foot vent combo/above the lower drain/return combo fitting. This results in both of the 2" combos for the drain laying on their side. Below is a maybe the world's worst sketch of the situation (with a view from the end, kinda), along with the standard island vent picture showing where I'd like to put the 45s.

Laying the lower combos on their side feels wrong, but I can't put a finger on what code it would violate. Thoughts?

-Matt

island_sink_bert_polk terrible drawing.jpg
 

wwhitney

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I think the upper 45s are fine. I did the same on my island loop vent to keep the drain line within the joist bay as it runs 20' across the basement.

On the lower 45s, can't you achieve the same left-right offset by either (a) raising the upper 45s or (b) just downstream of the combo where the foot vent drains into the drain, use two 45s horizontally to jog the drain at that point?

Cheers, Wayne
 

Hudsonmd

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I think the upper 45s are fine. I did the same on my island loop vent to keep the drain line within the joist bay as it runs 20' across the basement.

On the lower 45s, can't you achieve the same left-right offset by either (a) raising the upper 45s or (b) just downstream of the combo where the foot vent drains into the drain, use two 45s horizontally to jog the drain at that point?

Cheers, Wayne
Thanks for the quick reply!

The second set of 45s is more about the vertical offset than the horizontal. It reducing the vertical space needed for the combo at the bottom of the foot vent (and as a side effect also causes the horizontal offset). Pushing the drain further away from the block wall is a bonus (as it does shorten the drain run further downstream, though I didn't show that part), but not the real intent. It also raises the drain a bit, giving more height to drop on the way to the main stack.

Totally unrelated question (that I forgot to ask): The code for island vents states that the top of the loop can be constructed with a 45-90-45 set of fittings *or* a single piece. I'm wondering what single piece could be used for this? Maybe the lower half of a p-trap, inverted? I can't find anything about a minimum radius for the top of the loop...

Thanks,
-Matt
 

wwhitney

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The second set of 45s is more about the vertical offset than the horizontal.
Ah, so you want to minimize the height difference at the loop between the foot vent and the drain. If you use a street san-tee for the foot vent horizontal takeoff, going directly into a combo for the vent/drain connection, with the two fittings at 45 off plumb due to the upper 45s, is that height difference still too much?

Cheers, Wayne
 

Hudsonmd

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Ah, so you want to minimize the height difference at the loop between the foot vent and the drain. If you use a street san-tee for the foot vent horizontal takeoff, going directly into a combo for the vent/drain connection, with the two fittings at 45 off plumb due to the upper 45s, is that height difference still too much?

Cheers, Wayne
Oooo, that is a good idea. Can I use a san-tee at the bottom of the foot vent? If so, that would be a space saver for sure. In my head that had to be a long sweep (prolly 'cause all the pictures show it that way), but going from horizontal to vertical seems like it should be ok with a san-tee. I'll measure up that approach in the morning and see if it give me enough height.

So is the lower set of 45's a no-no, then? It feels a bit wrong, but seemed like it would be to code as far as I can tell.

Thanks again!
 

wwhitney

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Everything has to be arranged to drain out the drain. So the bottom of the vent side vertical of the loop could be a san-tee above a combo.

As to the extra 45s at the bottom, I can't say that it wouldn't be allowed, just that it's non-standard. You'd have to review the details of what the IPC has to say about island venting. I bet it would comply.


Cheers, Wayne
 

Hudsonmd

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I was rather shocked that such an odd fitting existed, but I just ordered a 2" x 1-1/2" x 1-1/2" street san-tee, which should be the perfect thing for this situation.

I also ordered a return bend that I'd like to use at the top of the loop instead of the 45-90-45 that seems to be the norm. A single fitting there makes sense to me, and it is also a bit more compact. Once again I don't see any reason it would violate the code, but I've never seen mention of doing this - anybody out there used a return bend for this application? Any feedback on whether it will pass inspection?

Thanks again, Wayne.
-Matt
 

Tuttles Revenge

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I was rather shocked that such an odd fitting existed, but I just ordered a 2" x 1-1/2" x 1-1/2" street san-tee, which should be the perfect thing for this situation.

I also ordered a return bend that I'd like to use at the top of the loop instead of the 45-90-45 that seems to be the norm. A single fitting there makes sense to me, and it is also a bit more compact. Once again I don't see any reason it would violate the code, but I've never seen mention of doing this - anybody out there used a return bend for this application? Any feedback on whether it will pass inspection?

Thanks again, Wayne.
-Matt
I've seen a return bend/p-trap U mentioned in code as an alternative, but don't recall where.

In my mind I believe that the intention is that there would be no Flat spots in that vent section so a U would appear to work to that intention.
 

Jeff H Young

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Just wondering why do all that when Virginia allows AAV ? At least I think they do
 

Terry

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Just wondering why do all that when Virginia allows AAV ? At least I think they do
Over the years I installed a ton of the Island Kitchen Sink Vents.
If you can do the AAV, and the rest of the home is atmospheric through the roof, I would now do an AAV when I can't run the vent straight up through the roof.

index.php


For this bath remodel, an AAV at the lav that vents the bathroom.
 
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