Does this dishwasher drainline need to be changed?

[AdrianMariano]

The disposer may be full, and or it may do other bad things, and or the sink and or the dishwasher may also do bad things. Cross-connections and backflows possible everywhere. Rarely happens but can be fatal, lethal, deadly. It can be a matter of life or death. That is what plumbing is about. In my view, it is more complex than electricity which is also extremely dangerous.

The above is kind of vague. I thought the concern was water flowing backwards into the dishwasher, which is supposed to be a clean area. Also I guess it would be really annoying if the dishwasher filled up with water to the level of the sink from siphoning. Open the dishwasher and you'd have a huge mess.

What other cross connection of backflow is there in this situation to worry about? I can't contaminate my water supply because the faucet is higher than the sink. I guess I can contaminate the sink. But that's about it.

Other than clogging the pipes, what "bad things" can the disposer do?

What "bad things" can the dishwasher do? I could imagine it somehow draining water continuously. Or maybe draining water that is full of debris and clogs the pipes. But if the latter is going to happen you're presumably better off having it go through the disposer since the disposer gives you a second chance to deal with the debris.

Look at any installation with NO disposer, and then look at my remarks as saying "can we do the same thing WITH a disposer present, by just not going through the disposer?" I am not a plumber so I ask without knowing the answer.

As I understand it, there are two ways to construct an installation with no disposal. One involves a high loop air gap and the other one involves an air gap on the counter top. I don't see a reason why you couldn't have a disposer and nevertheless connect the dishwasher drain to the second sink drain which doesn't have the disposer. But you'd still have the high loop air gap or the air gap on the counter.

Now it seemed that you were suggesting some third type of air gap, a "teed air gap below the sink but above the trap". I don't understand what this is. And it seems like as soon as the water level in the system rises above it (e.g. into the sink) then water will be able to siphon back into the dishwasher (or water will be pouring out of this mysterious under-the-sink air gap). So this type of air gap wouldn't be as good as the other two kinds at preventing siphoning back into the dishwasher.

 

[Geniescience]

sorry I'm not able to describe things in fewer words, and more precisely too.
Not being a plumber, i'd better let someone else point out in a few words what i cannot. I realize that my explanation was far from clear.

Check out the analogy of the garden hose trickling water out, and with its nozzle in a puddle. Has been described many times before; it's a vivid picture.

About the air gap, I'll find that diagram I keep on mentioning, where there is no disposer. I'm sure you can find it too. The Tee is nothign special at all, it is the only way to tee into a drain.

bye for now.

david

 

[Sponsor]

 

[Geniescience]

Dishwasher Branch Tailpiece

.... can still have an air gap! If the sink's P trap is several inches below the sink, just Tee your dishwasher drain in under the sink, several inches above its P trap. That is enough air space to do the job. The air is in the 1 1/2" drain pipe above the P trap.

That is what I have. The "T" has a slight slope to it. It's copper or brass. From there, a rubber hose loops high (from the Tee) and then down to the dishwasher.....

Adrian,
I found the thingie. It's called a Dishwasher Branch Tailpiece. Picture at this thread https://terrylove.com/forums/showthread.php?t=12532&highlight=dishwasher+branch+tailpiece

With it, you just high-loop to it; you don't put an air gap in the counter. Teeing in to the tailpiece like this eliminates the need for an air gap. The Tee itself IS an air gap.

david
edit (5:47 p.m.): why this was important was that I said I thought it was one way Not_To_Send_DW_Waste_Water_Through_ the_ Disposer. That may have been discussed in your other big thread.
2nd edit (36 hours later): a loop isn't higher than the flood rim of the sink so it isn't an air gap in plumbing terms. Under the right conditions it will let dirty water backflow into the DW.

 

[TedL]

I don't see how the tee could be an air gap. In the situation where the drain clogs and wastewater backs up into the sink, you ahve a cross-connection between the sink drain and the dishwasher drain.

That having been said, there is an air gap between the waste connection at the bottom of the dishwasher and the fill inlet on the side or top of the dishwasher. So, cross connections are prevented.

 

[Dunbar Plumbing]

Agreed TedL

geniescience,


Since you seem to be rewriting codes through personal opinion of what necessitates protection and what does not, explain to me what is the difference from your theory and that of a swimming pool full of water with a hose draped over the ledge and dropped to a lower elevation to create a siphoning effect.

High looping a dishwasher drain is a direct connection to the drain system.

Also, explain fluid dynamics and tell us how a larger mass of water can exert force on a small opening and produce enough pressure to elevate water to a higher elevation.


When you take your family out to eat this weekend, go back into the restaurant kitchen and observe the air gap that is installed on the dishtank; Then tell them you just hook it straight to the drain and watch the response from the health department.

 

[Dubldare]

... That having been said, there is an air gap between the waste connection at the bottom of the dishwasher and the fill inlet on the side or top of the dishwasher. So, cross connections are prevented.

One thing to remember is that the CLEAN dishes sit in the area below the water inlet's air gap. They can be fouled before there is an issue with the water supply.

 

[Geniescience]

uh-oh.

i guess i'll have to edit that last post to say things more cautiously. That is clear to me.

Before I go back and re-read it and figure out what I could have said that would have been a little bit better, I'll ask that you just spend a few minutes helping me and everyone else with the right words that explain most of the problem. "Anything worth saying can be said in ten or twelve words." Please don't be sarcastic and cynical. I'm not a dolt; I can admit a mistake; I'm not usually far out in left field.

David

 

[Jadnashua]

As I understand it, an air gap is just that, a break in the connection. If water tries to go backwards, it ends up going out the air gap rather than through the dishwasher drain hose. Now, this can cause a mess, but it is safer than having it back up into the supposedly clean dishes and you not knowing about it. How often does this happen? All it takes is once.

 

[TedL]

One thing to remember is that the CLEAN dishes sit in the area below the water inlet's air gap. They can be fouled before there is an issue with the water supply.

Absolutely. That's why I referred to "cross connections", and not "problems".

On the other hand, if I live in the house and the sink has backed up, and I go to unload the dishwasher and see/smell a pool of foul wastewater sitting in the bottom, I'm not going to just put the dishes in the closet or on the table.

At some point, rules can't protect people from their own stupidity/irresponsibility.

 

[chimmer]

I'm not sure if I can put in an air gap because I already have the sink (18 gauge stainless) and it doesn't have a hole for the air gap. I seem to recall reading that it was very difficult to make a hole in a stainless sink.

Ikea sells a small tool to put holes in stainless sinks http://www.ikea.com/ca/en/catalog/products/28512100/
I've used one and they take a while to make the hole but I think it was a much cheaper solution than a fancy hole saw.

 

[Jadnashua]

A hole punch like that is the manual version of what is used to punch holes in the factory...they have the advantage of many tons of hydraulic pressure, but they work. You still have to drill a smaller hole for the bolt to fit through, but with the punch for the larger size, it does make a nice clean hole.

 

[hj]

quote;
, i've not heard of an air gap you set on your sink. Sorry! But could you not mount said device underneath sink?

ALL air gaps "set" on the sink, and NONE of them can be installed in the cabinet under the sink, (at least not unless you want to flood the cabinet). A "high loop" is NOT a 'type' of air gap, it depends on the sink drain or disposer to create the vacuum breaker action, but they can only do it if the sink drain is not plugged up and full of water. The IKEA tool is the "hole punch" previously referred to.

 

[Mark Fritz]

If you can explain to me just how it would be physical possible for water in a clogged drain could rise above the level of the sink and into the looped washer hose, I will gladly eat crow. Now I realize as a professional you are required to follow local codes and use an air gap where code requires, you must admit that air gaps are not required everywhere. I sure don't want to start a stupid war over this, so this will be my last comment to this question.

 

[Mark Fritz]

If you can explain to me just how it would be physical possible for water in a clogged drain could rise above the level of the sink and into the looped washer hose, I will gladly eat crow. Now I realize as a professional you are required to follow local codes and use an air gap where code requires, you must admit that air gaps are not required everywhere. I sure don't want to start a stupid war over this, so this will be my last comment to this question.

Crow might not actually be bad. I believe that if you are running your dishwasher and the drain is plugged you can load up the system to the rim of the sink. At this point when the dishwasher stops discharging that slight height difference between the top of the countertop and bottom of same would be enough to get backflow into the dishwasher started. At this point siphoning would commence allowing the entire sink to empty into the dishwasher. I think this would also result in overflowing the dishwasher onto the floor. An air gap would prevent this completely.

 

[Mark Fritz]

Act

If you can explain to me just how it would be physical possible for water in a clogged drain could rise above the level of the sink and into the looped washer hose, I will gladly eat crow. Now I realize as a professional you are required to follow local codes and use an air gap where code requires, you must admit that air gaps are not required everywhere. I sure don't want to start a stupid war over this, so this will be my last comment to this question.

Crow might not actually be bad. I believe that if you are running your dishwasher and the drain is plugged you can load up the system to the rim of the sink. At this point when the dishwasher stops discharging that slight height difference between the top of the countertop and bottom of same would be enough to get backflow into the dishwasher started. At this point siphoning would commence allowing the entire sink to empty into the dishwasher. I think this would also result in overflowing the dishwasher onto the floor. An air gap would prevent this completely.

Actually siphoning can occur immediately. All that is required is that the water level be above the dishwasher T when the dishwasher stops discharging. So maybe I'll join you in that scrumptious meal.

 

[Mark Fritz]

sorry I'm not able to describe things in fewer words, and more precisely too.
Not being a plumber, i'd better let someone else point out in a few words what i cannot. I realize that my explanation was far from clear.

Check out the analogy of the garden hose trickling water out, and with its nozzle in a puddle. Has been described many times before; it's a vivid picture.

About the air gap, I'll find that diagram I keep on mentioning, where there is no disposer. I'm sure you can find it too. The Tee is nothign special at all, it is the only way to tee into a drain.

bye for now.

david

 

[Mark Fritz]

Dishwasher Branch Tailpiece

Adrian,
I found the thingie. It's called a Dishwasher Branch Tailpiece. Picture at this thread https://terrylove.com/forums/showthread.php?t=12532&highlight=dishwasher+branch+tailpiece

With it, you just high-loop to it; you don't put an air gap in the counter. Teeing in to the tailpiece like this eliminates the need for an air gap. The Tee itself IS an air gap.

david
edit (5:47 p.m.): why this was important was that I said I thought it was one way Not_To_Send_DW_Waste_Water_Through_ the_ Disposer. That may have been discussed in your other big thread.
2nd edit (36 hours later): a loop isn't higher than the flood rim of the sink so it isn't an air gap in plumbing terms. Under the right conditions it will let dirty water backflow into the DW.

sorry I'm not able to describe things in fewer words, and more precisely too.
Not being a plumber, i'd better let someone else point out in a few words what i cannot. I realize that my explanation was far from clear.

Check out the analogy of the garden hose trickling water out, and with its nozzle in a puddle. Has been described many times before; it's a vivid picture.

About the air gap, I'll find that diagram I keep on mentioning, where there is no disposer. I'm sure you can find it too. The Tee is nothign special at all, it is the only way to tee into a drain.

bye for now.

david

The reason that you cannot find the words to explain how your configuration works is because it doesn't work. Please stop advising it. In order for an air gap to be effective it has to be above the water level of a completely full sink. Picture in your mind what your air gap would look like when the sink is full with a clogged drain. It would look like a direct path for flow to the dishwasher which is exactly what we are attempting to prevent.

 

[Mark Fritz]

The reason that you cannot find the words to explain how your configuration works is because it doesn't work. Please stop advising it. In order for an air gap to be effective it has to be above the water level of a completely full sink. Picture in your mind what your air gap would look like when the sink is full with a clogged drain. It would look like a direct path for flow to the dishwasher which is exactly what we are attempting to prevent.

In fact the sink would probably never fill up with your configuration because it would be draining into the dishwasher and onto the floor.

 

[Mark Fritz]

As I understand it, an air gap is just that, a break in the connection. If water tries to go backwards, it ends up going out the air gap rather than through the dishwasher drain hose. Now, this can cause a mess, but it is safer than having it back up into the supposedly clean dishes and you not knowing about it. How often does this happen? All it takes is once.

As I understand it, an air gap is just that, a break in the connection. If water tries to go backwards, it ends up going out the air gap rather than through the dishwasher drain hose. Now, this can cause a mess, but it is safer than having it back up into the supposedly clean dishes and you not knowing about it. How often does this happen? All it takes is once.

Water is coming over the rim of your sink and onto the floor. I'm not sure if any water will come through the air gap thingy but let's observe that it would certainly be insignificant.

 

[Mark Fritz]

Water is coming over the rim of your sink and onto the floor. I'm not sure if any water will come through the air gap thingy but let's observe that it would certainly be insignificant.

What I'm saying is that your sink will be overflowing before any water comes out of your air gap fixture.