Dishwasher, Disposal and Single Basin Sink in Illinois

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Kowalsky

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Hi there folks, newbie here. Big fan of this forum and a DIYer with more than basic knowledge. I have probably never needed to register as all of my a questions so far has been answered but not this time. See, I have searched entire forum and found some info but only to assure that my way of thinking is good. Terry is probably tired of posting same picture of how dishwasher should be connected thru air gap to the disposal....Anyway here is my story:
Illinois: not allowed to connect DW to disposal and we dont want to install airgap.
Sink: removed double and installed single basin and disposal. Disposal is higher by 1-1/2 than wall drain so it's fine.
Because initially in 1995 they have installed double sink and there are two waste outlets in the wall so needles to say DW has been connected to the left basin and disposal to the right with DW with high loop under the counter.
I should have known better before I have started this renovation that DW will have no air break/air allowance for the p-trap to work properly if I connect it to the left drain outlet alone and therfore it will siphone and allow sewer gas to enter thru DW. AAV is not allowed as I thought of installing it on top of DW tailpiece. The only two things I on my mind are these.: 1)maybe there is a high loop in the wall connecting both drain outlets and averything is going to be OK 2) maybe I can run an under the top of sink connection between DW tailpiece and the inlet hole on the disposal unit for air allowance.....but it will only work if there is no water in the sink. I guess it is not inspector way of doing thing and sooner or later we will have to face inspector when selling the condo.
Other things: new slim line disposal is very powerfull - when I ran it with sink full of water, the water startem to leak from under the cap on the left side so Im afraid the dirty water from disposal may occasionally enter the DW...maybe it is the problem of how the pipes are connected inside the wall? I cannot open the back wall as 1)the sink cabinet has been alredy renovated 2) pipes are brass (I will not handle it myself) 3) speciall condo board authorization needed for all rough work. So my question is this. How to have the disposal and DW with DW properly vented but not thru airgap having single basin sink in Illinois without redoing in wall rough? The last option is to remove the disposal out of equation...
Once again I appreciate your help advice and answers
EDIT: attached photos
 

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Reach4

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"Other things: new slim line disposal is very powerfull - when I ran it with sink full of water, the water startem to leak from under the cap on the left side"

You said "Because initially in 1995 they have installed double sink and there are two waste outlets in the wall so needles to say DW has been connected to the left basin and disposal to the right with DW with high loop under the counter."

I don't know what the minimum height of a standpipe for a dishwasher is for Illinois. I don't know a good solution for you.

I presume the dishwasher has not been connected so far, or that the pictures were from before.

What is this cap, of which you write?
 

Kowalsky

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What is this cap, of which you write?
This cap is where left side of the double sink was draining to (including DW).

I am slowly giving up on this....I mean I understand physics and local codes based on the physics and it is just impossible to eat a candy and have a candy at the same time - what I want to say that without air gap it is not possible.
 

Jeff H Young

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my code requires connecting to an airgap but we can hook to a disposal with an airgap or to a sink tail piece with airgap.
Your code I doubt is vague you just need to figure out where you live and under which code you are and meet the code
 

Kowalsky

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I just called one friendly plumber with the license for IL. He said to mount a P trap and tail piece on the left drain and connect DW to it. I asked him how is it possible for the water to drain from DW with gravity if I cap the top of the tail piece and he said: normally....I think he did not understand my situation and therefore gave me unprofessional answer.
I just dont get it.....double sink and you drain DW with no problems and no airgap.....single basin sink with disposal and you are basically forced to use an airgap
 

Kowalsky

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Ok Like I said there is not much to do. Having second drain does not really help as there is no way for P Trap to work properly if no "room air" enters from the top. I ended up hooking up DW to disposal thru high loop - no air gap. Sure I have a hole in the top of the sink for accesories such as....soap dispenser or....air gap:) but I wanted air pressure switch for disposal which I have installed. If inspector wants air gap I will remove the switch and install airgap. I filled sink with water and ran disposal - absolutely no water enters DW discharge so its good.
BTW
If any one wants used disposal with hardware and used delta faucet 440-DST feel free to pm. Item location is Des Plaines IL. Needless to say its free.
 

John Gayewski

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Your dishwasher should be directly connected to a trap and then the trap goes onto that second pipe that you have capped. I don't know what you mean about not being able to gravity drain as the dishwasher has a pump. The vent for the trap is in the wall and after the trap. The hose for the dishwasher waste should have water in it at all times.
 

Kowalsky

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"Your dishwasher should be directly connected to a trap and then the trap goes onto that second pipe that you have capped. I don't know what you mean about not being able to gravity drain as the dishwasher has a pump."
You mean counting from the wall: trap->tailpiece with branch for DW capped on top->DW hose?
Doesnt that configuration cause siphoning (and drying) the trap, does it(because no air admittance from the top of tailpiece)?
"The vent for the trap is in the wall and after the trap"
Yes I know. I goes to the roof. It allows the water that is after p trap to drain. But what about the water before p trap? Do fixtures need "room air" for properly draining in the first place? Sink allows air to enter from the top, toilet too....for example when I put a straw in my drink it is going to fill with fluid. If I cap it from the top with my finger top and lift it up above the glass it is not going to drain unless I take my finger of off the straw top opening....so...Im afraid that DW is going to drain but may make bubbling noise at the end, or siphone dry the trap.

Also, the DW drain hose is small in dia. When connected to 1-1/2 pipe it will force the DW pump to work harder.

I mean that is my understanding:)
 

John Gayewski

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This order. Dishwasher, hose, trap, vent, drain. The water is pumped from the dishwasher through the trap into the drain. When the pump stops the water stops. Siphon can't form due to the vent after the trap. This is how illinois wants it done. Illinois section 890.710.
 

Kowalsky

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The hose for the dishwasher waste should have water in it at all times.
In that (particular) case I would not even need a P trap because water in the hose would prevent the sewer gas to enter my kitchen thru the DW. But unfortunately (fortunately) the P trap is required by code and it is required always.

So the ultimate question is: Will trap work properly (not drying out by siphoning) with vent after it and no air admittance to the fixture before the trap?
 

John Gayewski

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This picture is from my illinois code book. It doesn't really apply to what were talking about except they show the connectivity. This diagram is mainly to show the requirements for a floor drain to be presant in a commercial kitchen. There's another diagram showing a standpipe configuration.
Screenshot_20230610-160716_Gallery.jpg
 

John Gayewski

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I think if it didn't work they would change it, don't you?

A siphon only happens when there is no atmosphere present. The vent provides atmosphere. So you can only siphon as far as the vent opening.
 

Kowalsky

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Thank you for claryfing that. However..... The diagram you provided is "direct connection with floor drain located within 4 feet" (illustration D)which is not happening in my home (and nobodys home I guess). So yes, you are right about the fact that this doesnt really apply to what we talk about because I dont have floor drain in my kitchen :D It is allowed IF floor drain is presence. It is perhaps for commercial use. I have found also illustration C and as you see there is an air gap. The explanation of both illustrations is at 890.1010 which I also attached below. Residential DW is explained 890.770 also attached.
 

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Kowalsky

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A siphon only happens when there is no atmosphere present. The vent provides atmosphere. So you can only siphon as far as the vent opening.
Ok got it. Thanks for that. Makes sense. You got me on physics here. Which is good because I can use that second drain on the left. However air gap of some form is required for "by the book" and inspector in residential application.
 

Kowalsky

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After an hour or so I second my last thought when I said "makes sense" hahaha. Of course the DW will drain like you said John regardless of direct/indirect hookup......but.....with direct connection the water may siphone to the DW empyting p trap even if hose is high looped under the counter (Just like empying car gas tank "mouth to hose and suck" old school way). That is why the air gap is recommended. Maybe it is not enforced. I have worked as an electrician for many years, seen many houses and apts, new constr remodeling additions etc. I have seen it thru many phases from rough to finish and honestly I have seen an actual air gap on top of sink maybe twice.
 

John Gayewski

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After an hour or so I second my last thought when I said "makes sense" hahaha. Of course the DW will drain like you said John regardless of direct/indirect hookup......but.....with direct connection the water may siphone to the DW empyting p trap even if hose is high looped under the counter (Just like empying car gas tank "mouth to hose and suck" old school way). That is why the air gap is recommended. Maybe it is not enforced. I have worked as an electrician for many years, seen many houses and apts, new constr remodeling additions etc. I have seen it thru many phases from rough to finish and honestly I have seen an actual air gap on top of sink maybe twice.
The dishwasher pump would have to be higher than the waste outlet for a siphon to work.
 

Kowalsky

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The dishwasher pump would have to be higher than the waste outlet for a siphon to work.
If the pump was higher it would siphone of course toward waste. But the pump is lower so.....it still may siphone but towards the DW. Not necessarily, not "for sure"....but it might. That is why the air break is needed. Not only to stop DW being contaminated with bacteria when hooked to disposal, not only to prevent water build up and damage when drain is clogged, but also to allow water sitting in p trap without siphoning either way. But because the tailpiece is long and large in dia comparing to DW hose I dont think it will siphone to DW.
Here is what Im going to do: on Mon I will do as you say John. I will try to observe how water behaves when draing the DW and I will get back at you. Thank you John for sparing your time with me. Enjoy the Sunday.
 
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Kowalsky

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This is how I did.
The DW drains fine. No water is moving back toward the DW after draining is over, although I have to say that the tailpiece is full of water. No funny bubbling noises when draining nor after. If I could only somehow let the air come inside thru that cap in top (in safely professional water tight manner) that would be ideal solution in my case. I though about 3 things: 1) remove the cap and connect top of tailpiece with airgap (adapters) which I dont want on top of my sink 2) remove the cap and connect it to DW inlet on disposal unit with a rubber hose and barb fitings 3) remove the cap and install AAV. Only #1 would probably meet the inspector demands.
EDIT. Just to clarify....the DW is connected directly to that capped tailpiece.
What do you think about water sitting in that tailpiece? Does it mean that there is a pressure in that setting? Something to worry about?
 

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Reach4

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I don't think IL allows AAVs, but I could be mistaken.
Level of the water in the tailpiece should match the elevation of the inside bottom of the trap arm (the part that feeds into the wall).
 

Kowalsky

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I don't think IL allows AAVs, but I could be mistaken.
Level of the water in the tailpiece should match the elevation of the inside bottom of the trap arm (the part that feeds into the wall).
You are right. The water does not levels because no air is allowed. Question to John: is this the setup that you were talking about?
 
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