yet another island sink vent question

[vmplumbing]

hello again!!

i was wondering if the height of a island vent loop was crucial



i have a customer who wants a deeper sink, and the only way to make this work really is to lower the height of the peak of the loop...currently about 2' above the lateral.

can i lower this six or so inches without compromising the vent?

[jadnashua]

I don't think so...otherwise it could fill up with water and block any air exchange. Wait for the plumbers...it is probably covered in the code. Have you read it?

[Terry]

This passed inspection in King and Snohomish County,

The code says something about as high as you can.
So if it's as high as you can, I guess that's good.

The "foot" vent drains the water if it gets too high, and the cleanout lets you keep the vent clear.

[vmplumbing]

thanks guys!!

ahh yes, the code book--i found it under a stack of popular mechanics, guitar players, and playboys

909.0 in the UPC--it says as high as possible, but not less than the drainboard height.

gotta love the wording in the code...a pox on the author

the existing island vent isn't quite to standards...if i don't touch it and instead advise the customer to go with an 8" sink depth (rather than 10" which would require replumbing the vent) we can probably have the existing vent "grandfathered" and accepted at inspection.

thanks again for your swift responses.

[hj]

Depending on where the obstruction is, the loop vent can become a secondary drainage, and if it is below the level of the sink bottom, it will drain without the customer knowing they have a problem, until it also plugs up, then they will have a major problem, actually two of them. With a true island sink it is impossible to install it above the drainboard level because that is above the island's counter top.

[jadnashua]

Well, often, but not always. There are a lot of multi-level islands out there, and with one of those, you could get the loop above the rim.

[frenchie]

I'm not following why swapping the sink should affect the loop height. Is the loop under the bottom of the sink?

True, you generally can't get it above the fixture's flood plane w/o a multilevel island; but the loop should be as high as possible, i.e. just beneath the countertop. So it should be beside the sink, not under it.

If the top of the loop is under the bottom of the sink, then it's not even a loop vent, just a double drain.

[vmplumbing]

yeah, it's touching the bottom of the existing sink...sink has 8" depth.

it's original equipment, probably a 40 year old house.


right now i'm tryin' to talk the customer into forgetting about a 10" deep sink, this way i won't touch the existing DWV and that will have a good chance of getting grandfathered.

the homeowner is acting as his own G.C.

he is going to try to have an inspector do a pre-inspection, to see what will fly...

[GrumpyPlumber]

the homeowner is acting as his own G.C.

Those are always the most time consuming, no insult to homeowners intended.
It sounds like the current vent is under the actual basin, if so - I'd talk to the "GC " about making room for the bow (loop).

[vmplumbing]

so far, he ain't havin' none of that regarding accomodating a code vent loop.

in my opinion, we could increase the depth of the cabinet by a few inches and that would do the trick.

he does not want to do this.

[GrumpyPlumber]

so far, he ain't havin' none of that regarding accomodating a code vent loop.

in my opinion, we could increase the depth of the cabinet by a few inches and that would do the trick.

he does not want to do this.

Been right in your very shoes.
I told the homeowner that the inspector would fail the existing piping.
I also explained that my time after being failed would be additional because I'd warned.
After the inspection when the piping was failed, my time was extra.
You might not get failed, but I'd be sure to cover yourself in case.

[vmplumbing]

I told the homeowner that the inspector would fail the existing piping.
I also explained that my time after being failed would be additional because I'd warned.

yup. i think that's where this is headed.

[patrick88]

so far, he ain't havin' none of that regarding accomodating a code vent loop.

in my opinion, we could increase the depth of the cabinet by a few inches and that would do the trick.

he does not want to do this.

Well he could waste his and your time($$) saying I'm the GC and you need to do what I say. This is not much different when a regular customer pulls the same crap. I would put my foot down and let him know he is making a big mistake not doing it by code.

[froddan]

Terry, do you or anyone else know if an AAV is allowed in King County, WA?
This is for a kitchen sink located in an island.
Pros, and cons compared to your work displayed here?

[construct30]

My understanding of using an AAV is that they are never allowed to be used below the flood plane of anything, so in an island no, unless you want to put it above the counter top. Our inspectors never want to see them. Update we have a new inspector that say OK to AAV as high as possible.

Our local inspectors say that as high as possible means the loop almost touching the counter top on an island. They are very hard on islands for plumbing and wiring here. They say if you want an island then build it to suit the codes.