Thanks everyone for the sage advice so far... I'm putting an island with the sink, dishwasher, and garbage disposal in my kitchen and I'm pretty sure I understand what needs to be done... but have just a couple questions.

My kitchen is above a finished crawlspace, so I have plenty of room to work beneath. I'm planning on dropping my 1 1/2" vent and drain pipes (from the loop vent) from the island, run them 6 feet to the wall of the crawl, take an easy 90 degree turn, then run 10 feet to the aux vent stack. I plan to make sure I have 1/4" drop per foot of pipe along both runs.

I can't go straight from the island to the stack because there's duct-work in the way, so making the turn seem to be my best option.

Will this work? I'm most concerned that running 16' with a right angle might be too long or that the 1 1/2" pipe may not be big enough for running a sink, dishwasher, and disposal.

Thanks for your help!
-Brian

Loop vent should be 2". The 16' run with 90 should be fine as long as you maintain the upslope and install clean out the each side. That vent connection should be above siphon level. Therefore, you should come up the wall and connect it at about 4' high.

( Hey, those "loop vents" - quite a contraption, aren't they... :D )

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I'm most concerned that running 16' with a right angle might be too long or that the 1 1/2" pipe may not be big enough for running a sink, dishwasher, and disposal.

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The right angle,( 90 degree bend I would change to a sweep or (2) 45 degree fittings.
I would also increase the drain line to 2 or 3 inches,( in my area we went to a 3" drain line from the kitchen because of all the solids from the garbage disposal.) the vent can remain at 1 1/2". You have options about the return vent. If you can get it past the inspector you could install a AAv under the cabinet,(see image) otherwise you can do a regular island sink hook up,(see image).
Good luck, tom

Tom, how about if he gives it better upslope ? Like 1" per foot ?

Ok, I'll definitely bump up the drain line to 2". The aux stand pipe (I think that's the right term) that I'm tapping into is also 2"... the old sink used to drain into it, so I'm thinking that going up to 3" wouldn't be that advantageous. The main 4" stand pipe isn't too far away, I could instead cut into that and run 3" drain, think that would be advisable? Maybe run drain to the main 4" and vent to the aux 2"?

I'll also change my 90 degree to two 45s, great idea.

Milo, I didn't understand your comment about getting the vent raised above siphon level. Would you explain that some more.

Thank you!

This detail pertained to the vent part of your installation. The actual vent connection should take place on existing vertical pipe and about 4' above the floor lever. In other words: you run the vent horizontally, then you'll turn it up and to the wall and make your connection there.

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The main 4" stand pipe isn't too far away, I could instead cut into that and run 3" drain, think that would be advisable? Maybe run drain to the main 4" and vent to the aux 2"?

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Whatever's the easiest for you. That's what this site's all about. We also increased our kitchen to 3" because much of the time the washer and kitchen branch is combined before it connects to the main. Good luck, Tom

3" drain for kitchen sink is a great idea !

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Originally Posted by Milo Dolezal

3" drain for kitchen sink is a great idea !

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Our local codes mandated this change last year. Also I wanted to add that it would be a good idea to install a cleanout tee just under the stub out tee.
You'll thank me if you ever have to snake a blockage. Good luck, Tom

Cleanout tee, got it.

Forgive me for being a little dense... I just want to make sure that before I go cutting a section out of the aux stack, I'm doing it in the right place.

I'm patterning my plans aftetr this article (with the adjustments we already mentioned):

Black & Decker Power Tools

The section of the stack that I'm was planning to cutting into is in the crawl space. There's really no place that I can tap into that's 4' above the floor, not without cutting out drywall somewhere anyway. The crawlspace is about 3' tall.

Thanks!

Why not just simplify the job and install a AAV? Sound like a plan? Tom

That was my first thought... but checking the IL building code I found

Section 890.1480 Types of Fixture Trap Vents
- Mechanical Vents. Mechanical devices shall not be installed in lieu of vent piping

Additionally...

Section 890.1600 Special Venting for Island Fixtures
The returned vent shall be connected to the horizontal drain through a wye-branch fitting and shall be provided with a vent taken off the vertical fixture vent by means of a wye-branch immediately below the floor and extending to the nearest partition and then through the roof to the outside atmosphere or may be connected to other vents at a point at least 6 inches above the flood level rim of the fixture served.

I found this diagram in IL code for island venting...

http://www.ilga.gov/commission/jcar/...s/image010.gif

If I'm finally absorbing this right (finally), if the vent is dedicated for the island, you just run it to the wall, up, then out. But, if I'm tapping into another vent stack (wet or dry), I need to tap that vent stack at least 6" higher than where my sink would overflow.

Milo, you really got me thinking on this one... yeah, loop vents, quite a contraption!

I think I finally get it.. yeah?

Looking at the Black & Decker pictorial regarding loop vent installation... Looking at their photo #16: It would be against the code in my area for the following reasons:

1. Vent is connected to main2" stack drain/vent below the floor level ( aka anti-siphon level). This pipe should be acting as vent, not overflow drain.
2. They used 45 Y and 45 elbow to create Comby fitting.

Your sketch posted in your post #12 is what we would consider (almost) correct loop-vent installation in So.California - even though majority of Inspectors ask for 2" vent, not 1 1/2". Also, in your sketch, there are no clean-outs. In my area, we would have to install total of 3 clean-outs.

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Originally Posted by speedball1

( in my area we went to a 3" drain line from the kitchen because of all the solids from the garbage disposal.)

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Sounds like overkill to me, Tom.

I can't see the discharge from an 1-1/2" trap generating enough scouring action within the 3" pipe to sufficiently move the solids along.

The 1.6GPF for low consumption toilets adopted back in the 80's was finally settled on after all of the code writing authorities deemed it a barely acceptable minimum to scour solids through a 3" drain line.

Even with a plunger, you aren't going to send enough waste water with enough velocity to create the necessary scouring action to clear solids from a 3" pipe with an 1-1/2" trap.

*shrugs*

Just my two pence.

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Sounds like overkill to me, Tom.

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Growler: Not when you factor in a washer station on the same branch. Most of our kitchens and washers are on the same line and you know how garbage, grease and fiber will mat up into a clog. Any how it works for us.

Brian:

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If I'm finally absorbing this right (finally), if the vent is dedicated for the island, you just run it to the wall, up, then out. But, if I'm tapping into another vent stack (wet or dry), I need to tap that vent stack at least 6" higher than where my sink would overflow. I think I finally get it.. yeah?

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Close, but not quite! If you revent back to another stack that has a fixture draining into it you must tie back to the that fixtures vent at least 6 inches over that fixtures flood rim not the sink you're installing. Got it now? Good luck, Tom

I woke up this morning thinking about the bathroom that's a 1/2 story (I'm in a split level) above that shares the same wet wall... and thinking the same thing that you just mentioned.

There are some guys putting new flooring in the kitchen right now... but as soon as they're done, I'm going to check to see if the aux stack is being used by that bathroom or if the bathroom is draining to the main stack.

If the bathroom shares the stack, I'll tie in at least 6" above that sink. But, if the aux stack was dedicated to the old kitchen sink, it'll save me a few feet and I'll tie 6" above the flood rim of the of the new kitchen sink.

I'll also put cleanouts on my turn in the crawl, one before the drain goes up, and one in the loop vent (similar to the picture in speedball1's #3 post). Can you have too many cleanouts? (maybe that's a different thread!)

You guys have been really helpful! Thank you so much.

I think every plumbing fixture should have clean out. It doesn't "hurt" the system. As far as your loop-vent goes - and according to So.Cal Code - you should have 3 clean outs. I marked location of clean outs with red dots into your sketch:

Milo works under a very strict code that the rest of us find to be, 1) restrictive, 2) more costly in both labor and material and a all around pain in the a$$. Case in point. Look at Milos drawing. I can see where It would be handy to have a cleanout on the drain line. That makes good sense. But what don't make any sense at all and simply adds to the cost without giving you the least bit of advantage is installing two cleanouts on a dry vent that the only thing in the pipe to clog up is air.( Do you guys have to install cleanouts on ALL dry vents?) And that's just one silly madate. I could write a book about the others. Growler works under the same ridged code. Sure am glad us east coast guys don't hafta hassle with UPC. Cheers, Tom

Tom, each clean-out takes care of its own section of pipe. The third clean-out ( on dry vent) is there in case the sewer backs up, solids fill up-sloping horizontal section of vent, and as result - blockage won't drain out clogging horizontal vent.

Each 2" ABS clean-out is $3.79 at Home Depot. It is not such an expense to insure all your pipes are accessible with snake. But I have to agree with you: I also think it is overkill.

Overkill Milo? I think some of your codes are downright laughable, not to say just plain dumb. But then I regard some of ours the same way. When's the last time you ever heard of a hose with a open end laying in a mud puddle turned on and running all by itself when all of a sudden the city main lost pressure and the water began to flow backward in the main setting up a suction that pulled all that muddy water back in the main? Never? Nether have I. But the powers that be prevented us from installing backflow preventers on all hose bibs, (which perform the very same function for a lot less $) and forced every one to install expensive brass backflow preventers on all our new construction at the water meter. Just another silly rule that costs the home owner more. Sort of like your UPC isn't it? Cheers, tom