# Backflow for Residential Dish Washers



## Regulator (Aug 20, 2009)

Is a backflow preventer required on the supply to a residential dishwasher in your area? If so, what type?


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## TheMaster (Jun 12, 2009)

Not here.


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## gusty60 (Oct 21, 2008)

High loop only here.


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## ROCKSTARPLUMBER (Dec 14, 2008)

not here.


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## kfosh (Jun 17, 2008)

dishwasher air gap on the top of my sink countertop. here in west texas


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## Ron (Jun 12, 2008)

Only high loop under sink is required.


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## Regulator (Aug 20, 2009)

kfosh said:


> dishwasher air gap on the top of my sink countertop. here in west texas


I have seen a picture of those. So is it mandatory there?


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## uaplumber (Jun 16, 2008)

High loop


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## Protech (Sep 22, 2008)

nope


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## Regulator (Aug 20, 2009)

http://www.terrylove.com/wwwboard/messages/1641.html

Sketch of counter top air gap.


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## kfosh (Jun 17, 2008)

the company i worked for a few years back did dishwashers for sears hd and lowes the inspectors in both towns said when we change out a d/w a counter airgap was required. Was doing a remodel a year or so back and the inspector was checking mechanical i hadnot called for a plumbing final. Kitchen was finished but airgap was not in hole he asked me if i was going to put a airgap in and i said you know it. That was all i needed to do before i call for an inspection he checked the plumbing in the house and gave me a green tag and went on his way before i got under the cabinet and installed it


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## DUNBAR PLUMBING (Sep 11, 2008)

Air Gap required in KY.

Same requirement required on commercial applications nationally.


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## M5Plumb (Oct 2, 2008)

Airgap in Washington, looped up in Oregon. No back flow device.


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## Tankless (Jun 12, 2008)

I believe the OP was asking about the water SUPPLY to the DW. if that's the case, no. On the discharge an air gap is required. But on most custom jobs they get thrown in the trash, replaced with a disposer air switch and a high loop is used. I don't know why really since most new / nicer DW's are trapped as it is.


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## Regulator (Aug 20, 2009)

Tankless said:


> I believe the OP was asking about the water SUPPLY to the DW. if that's the case, no. On the discharge an air gap is required. But on most custom jobs they get thrown in the trash, replaced with a disposer air switch and a high loop is used. I don't know why really since most new / nicer DW's are trapped as it is.


Tankless, that is correct. Thank you. :yes:

Although an air gap will prevent backflow from the sanitary, there is still the issue of the water within the dishwasher itself entering the potable water supply under a back-siphonage condition. Although remote, the possibility does exist.


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## Airgap (Dec 18, 2008)

Ron The Plumber said:


> Only high loop under sink is required.


Same here.


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## Ron (Jun 12, 2008)

No additional backflow devices required on DW here.


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## Airgap (Dec 18, 2008)

oops, didn't read far enough. No cross conn. protectin on the water supply here.


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## SlickRick (Sep 3, 2009)

High loooop.

No supply protection


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## undispised (Nov 20, 2008)

high loop


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## Cal (Jun 17, 2008)

Regulator said:


> Tankless, that is correct. Thank you. :yes:
> 
> Although an air gap will prevent backflow from the sanitary, there is still the issue of the water within the dishwasher itself entering the potable water supply under a back-siphonage condition. Although remote, the possibility does exist.


 Ok ,, but has ANYONE seen that ??:no: Not required here either . Loop on the waste


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## pauliplumber (Feb 9, 2009)

Although rare I have seen a few here. It's actually in our code book to install an air gap. One of the few things that's code here, that none of the inspectors enforce. We have this one inspector here, who's a real hard ass, he will fail you if he doesn't like your haircut. Everyone in my area know's who I'm talking about. I installed a dishwasher in his town once, called and asked him if he wanted an airgap, and even he laughed and said no.

On the water feed no backflow needed here.

On the drain you need to loop it as high as possible.


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## grandpa (Jul 13, 2008)

Regarding the WATER SUPPLY.....no code requirement here for backflow prevention. I suspect the rational is that the water outlet INTO the DW is above the flood rim of the unit. Just like swimming pools can avoid a backflow if the put the fill line 6" above the level of the cove.


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## Regulator (Aug 20, 2009)

grandpa said:


> Regarding the WATER SUPPLY.....no code requirement here for backflow prevention. I suspect the rational is that the water outlet INTO the DW is above the flood rim of the unit. Just like swimming pools can avoid a backflow if the put the fill line 6" above the level of the cove.


When the door of a standard residential dishwasher is closed it creates a water tight seal. Dependency of the connection being above the flood level rim indicates to me that the backflow preventer in use is an air gap. An air gap shall not be located in a noxious environment. When the dishwasher in operation, I am not certain that the air gap is acceptable.

Is anyone aware of a code requirement that stipulates how a piece of equipment is to prevent backflow downstream of the connection to the water distribution system?


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## grandpa (Jul 13, 2008)

Regulator said:


> When the door of a standard residential dishwasher is closed it creates a water tight seal. Dependency of the connection being above the flood level rim indicates to me that the backflow preventer in use is an air gap. An air gap shall not be located in a noxious environment. When the dishwasher in operation, I am not certain that the air gap is acceptable.
> 
> ?


 
I believe what we have here ( no pun intended re: high-loops!) is a LOOPHOLE!


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