Island sink loop vent

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Vlad-NY

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Can someone explain why the loop part (highlighted in green in the attached pic) of the drain that is inside the kitchen cabinet has to be all the way to the countertop line before looping back down under the floor?

Can the loop be a few inches below countertop line (maybe just a few inches above the sink drain but not to the countertop line?) so that I don’t have to cut my kitchen cabinet? I wanted to place my piping in the back of the cabinets but to accomplish that I would have to cut a structurally important panel and I don’t want to do it.

Is it absolutely necessary or required to be at max height under countertop?

If it is absolutely necessary to go to the max below countertop then I will have to find a place the piping in a slightly different position in the cabinet which allows not to damage the cabinets structural integrity.
 
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Reach4

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Can someone explain why the loop part (highlighted in green in the attached pic) of the drain that is inside the kitchen cabinet has to be all the way to the countertop line before looping back down under the floor?
To minimize the chance that a blockage in the drain line would go unnoticed, or at least that would be one reason.
 
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Vlad-NY

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To minimize the chance that a blockage in the drain line would go unnoticed, or at least that would be one reason.

Thanks.

But how does that work exactly? How does height of that loop matter between higher versus lower given it is above sink bottom?

Blockage in the drain line means water does not flow and sink fills up like a tub and water spills over the counter.

What does all of this have to do with height of the loop?

Maybe the goal of the vent in kitchen islands is to serve as a backup drain once the main drain clogs? If that’s the case how do you find out there was a blockage?
 

James Henry

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Maybe the goal of the vent in kitchen islands is to serve as a backup drain once the main drain clogs?
NO..... As long as the crown of the vent is a few inches above the bottom of your sink you'll be able to tell if you have a clogged drain so if your able to do that then that's what I would do, if someone forces you to change it, it's no big deal to change it.

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Sylvan

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I personally hate island sinks because of the venting

A normal vent is locate 4" above the highest fixture to p prevent the waste from entering it

If for example the 45 deg ell was blocked prior to entering the Y and the vent was lower the waste would then be forced to use the vent as a waste line

By having the island sink vent installed high as possible the waste in case of a stoppage shows up in the sink as already stated
 

Sylvan

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NO..... As long as the crown of the vent is a few inches above the bottom of your sink you'll be able to tell if you have a clogged drain so if your able to do that then that's what I would do, if someone forces you to change it, it's no big deal to change it.

If an inspector should "force you " into redoing it the next job you file changes are the inspector will be on the lookout for other things you may have overlooked

NYC plumbers and master fire suppression licenses were allowed to do self certification.

Even gas piping we could do self certification, roughing and finish

Once in a great while an inspector would drop by and look around if a if they saw something we had to redo we lost the self certification privilege

Sometimes it just pays to go above code requirements as codes set the minimum requirements
 

James Henry

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If an inspector should "force you " into redoing it the next job you file changes are the inspector will be on the lookout for other things you may have overlooked

NYC plumbers and master fire suppression licenses were allowed to do self certification.

Even gas piping we could do self certification, roughing and finish

Once in a great while an inspector would drop by and look around if a if they saw something we had to redo we lost the self certification privilege

Sometimes it just pays to go above code requirements as codes set the minimum requirements
Since he's a DIYourselfer I didn't think he was to worried about his reputation he just didn't want to butcher his cabinet if he could help it.
 

Vlad-NY

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I personally hate island sinks because of the venting

A normal vent is locate 4" above the highest fixture to p prevent the waste from entering it

If for example the 45 deg ell was blocked prior to entering the Y and the vent was lower the waste would then be forced to use the vent as a waste line

By having the island sink vent installed high as possible the waste in case of a stoppage shows up in the sink as already stated

So... to conclude, this is my understanding...

The point of the loop part to be maxed out below the countertop is so that it gives more time to the chef that there is a clog.

The loop part can be anywhere above the sink bottom but if it is let’s say only an inch higher then the water will start flowing into the vent drain and the cook doesn’t have a clue there was a clog versus if it is 2 inches or higher above sink bottom gives a lot more time to determine there is a clog.
 

James Henry

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So... to conclude, this is my understanding...

The point of the loop part to be maxed out below the countertop is so that it gives more time to the chef that there is a clog.

The loop part can be anywhere above the sink bottom but if it is let’s say only an inch higher then the water will start flowing into the vent drain and the cook doesn’t have a clue there was a clog versus if it is 2 inches or higher above sink bottom gives a lot more time to determine there is a clog.
That's correct. BTW, the plumbing code does not demand the crown of the vent be up against the bottom of the cabinet. do some research on the internet.
 

Vlad-NY

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That's correct. BTW, the plumbing code does not demand the crown of the vent be up against the bottom of the cabinet. do some research on the internet.

Thanks a lot. I think it is like 4”.

And given my sink will be 10” deep I can do it no problem without cutting my cabinet.

I am trying to fit the piping (marked in blue) in the back of the cabinet without cutting the red piece. Hence all of my above questions.
 

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Vlad-NY

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Water will stay at that level until you clear the drain.

Yes. But that is true only if faucets are off.:)

Actually no I take it back. The water will flow into the vent if faucets are on. And it is hard to know there is a clog.

So the higher the loop the better.

Thanks a lot
 

Vlad-NY

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one more question

Can I have the vertical section that I circuled in red be size 1 1/2 “ (blue) and everything below floor level 2” (green)

I know everyone will say it must be 2 “ connected to sanitary tee 1 1/2” at the point of the trap. But a 2” pipe doesn’t fit in the back of my cabinet or I have to drill the bottom panel.
 

James Henry

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Here is the best advise I could give you. Go to your city's website and look up what plumbing code your city has adopted then search for that specific plumbing code on the internet, they are all virtually free to read online. the codes are different all over the country.
there is a section on island vents in every code you just have to look in the " VENTS " section of your particular plumbing code.
 

Terry

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I don't know of any codes that let you have a 1.5" to to that last santee. Sure you can do it, but is it being inspected? Kitchens used to be run with 1.5" so yes, it will work, but not pass an inspection.

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Even this old kitchen rough was 2" to the santee and then went 1.5" on the vent.
It did plug up one time at Thanksgiving when too many potato peelings were put down the disposer at once. It does pay to have newer disposers that will chip it small and make sure you're running water the entire time. It looks like I'm soldering a joint.

They like the Island Vent to go as high as you can. And sometimes that isn't all that high. They do have the foot vent for that reason.

sink_rough_island_b.jpg
 
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Vlad-NY

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I don't know of any codes that let you have a 1.5" to to that last santee. Sure you can do it, but is it being inspected? Kitchens used to be run with 1.5" so yes, it will work, but not pass an inspection.

terry-10431-kitchen.jpg


Even this old kitchen rough was 2" to the santee and then went 1.5" on the vent.
It did plug up one time at Thanksgiving when too many potato peelings were put down the disposer at once. It does pay to have newer disposers that will chip it small and make sure you're running water the entire time. It looks like I'm soldering a joint.

They like the Island Vent to go as high as you can. And sometimes that isn't all that high. They do have the foot vent for that reason.

sink_rough_island_b.jpg

Terry,

Thank you. And yes, it’s not being inspected.

My cabinets have open space in the back, which my guess is designed for piping /wiring (see pics), but only 1.5” pipe / san tee fits in there.

The vertical section of 1.5” pipe, coming down from san tee that by code is to be 2” is only 2’ in height or less. Then directly under floor I have 2” waste lines.

How likely that vertical section will clog?

Thanks again
 

Vlad-NY

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Terry,

Thank you. And yes, it’s not being inspected.

My cabinets have open space in the back, which my guess is designed for piping /wiring (see pics), but only 1.5” pipe / san tee fits in there.

The vertical section of 1.5” pipe, coming down from san tee that by code is to be 2” is only 2’ in height or less. Then directly under floor I have 2” waste lines.

How likely that vertical section will clog?

Thanks again
I want to buy food disposer, plus 10” deep sink, so it leaves about a foot maybe above floor in 1.5” versus 2”.
 
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