Kitchen island sink drain into basement washing machine drain

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Martin.D

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Hi,

First post on this forum. I am building a cottage with my dad and i have naively decided that this DIY project would include the plumbing... I am in Québec, Canada (sorry for my rusty english).

My question is... I have a kitchen island sink on my first floor and I am wondering how to drain it to my basement. This sink is on the wrong side of my beam so the 2 inch drain can't reach my waste stack (I don't want to drill a hole bigger than 2" in my beam)... However, the sink is above my washing machine basement drain, so I figured out I would try to drain the sink in this drain which connects to my main sewer line below the concrete. Can I ???

I joined pictures of what I am planning to do. I haven't seen anything like that in my research and I know it looks weird, but I haven't seen a clear rule that forbids this kind of arrangement either. My island sink will be vented with a loop vent circuit (as shown on the drawing bellow). Both the vent of the island sink and the washing machine will be 1 1-2" and will be redirected horizontally in my floor joists and pass through my beam (2 inch hole) and meet above the flood level of the island sink and through my roof. I Hope everything is clear. Am I all wrong? I believe the P-trap won't be siphoned with the vent... what about suds pressure zones?

Thanks a lot for your help. This forum has been very helpful in the past weeks.

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Martin.D

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So here is what I am trying to do for my kitchen island sink. As you will notice in the pictures attached, the drain and the vent are going in different directions. The "horizontal drain" is heading towards the washing machine (there is a beam there as well but it is not in the way), and the horizontal vent has to do 6 feet horizontally before hitting my main LVL beam. So... I tried to do like on the diagram in my first post, but i don't have enough space vertically, so I had to tilt the fittings in 45° angle to make it work...at least to try!

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As I just mentioned, my problem is that I don't have much room under my 12" joists, as it will be a finished basement and also because I need my vent to slope upwards for 6 feet and reach the middle 3rd of my 12" beam (in other words, the hole can't be higher than 8 inches) as shown in the figure below.
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So, if my hole diameter is 2 inches, the distance is 6 feet and my horizontal vent slope is minimal (1/8"/ft)... the bottom of the horizontal vent has to start at a maximum of 5-1/4 so it finishes at 6 inches once at the beam. (6x 1/8" = 3/4 ")

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From what I have seen online, you have to use wye + 45 or combos make this kind of venting system. Has shown below, with those fitting, even if the are tilted at 45°, it's just too high and there is no way i can reach my beam at the right height. I also included another set up i made which is compact enough, but I really doubt it is legal.

TILTED COMBOS and WYE +45: I am at 6-3/4" (1,5 inch above the maximal height)

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SAN-T + 90 spigot

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At this point... any ideas how to do this thing, or should I just use an AAV? I am afraid that a AAV won't be enough to vent the 8 foot vertical drop of the sink.

Many thanks!

Martin
 

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Jeff H Young

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following your code should be ok I never heard an AAV wont work properely in this type case But Im not into AAV either. But if you cant legaly build an island sink due to structural constraints You have little option
 
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