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Old 09-08-2009, 06:18 AM
 
2 posts, read 15,737 times
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I purchased a used Whirpool dishwasher. It has a 1" drain below narrowing to a 7/8" short flange. The sink trap also has a 7/8" fitting. I bought a rubber adapator that fits over the 7/8" flange onto the the 1" fitting of the dishwasher. (the 7/8" section of the dishwasher drain is so short a clamp will not hold it.)So now I have to connect the 7/8" section of the adaptor with the 7/8" drain hose. So I have a 1/2" nipple connecting the adaptor and the 7/8" hose. A friend mentioned this might cause an "air brake" problem. Any ideas???
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Old 09-08-2009, 07:40 AM
 
Location: Houston, Texas
10,447 posts, read 49,508,076 times
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Quote:
Originally Posted by beatnick fly View Post
I purchased a used Whirpool dishwasher. It has a 1" drain below narrowing to a 7/8" short flange. The sink trap also has a 7/8" fitting. I bought a rubber adapator that fits over the 7/8" flange onto the the 1" fitting of the dishwasher. (the 7/8" section of the dishwasher drain is so short a clamp will not hold it.)So now I have to connect the 7/8" section of the adaptor with the 7/8" drain hose. So I have a 1/2" nipple connecting the adaptor and the 7/8" hose. A friend mentioned this might cause an "air brake" problem. Any ideas???
Though I installed several thousand dishwashers over the years I think you lost me. I think you worry putting on an extention on the drain house might cause some backwash problem. I never heard of an air brake. There is a one way valve preventing free falling down hill falling waste water from re-entering the DW. I say down hill because the sink drain is always higher then the waste line from the DW.
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Old 09-08-2009, 08:59 AM
 
3,020 posts, read 25,672,075 times
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Default Air brakes are on trucks and trains.

Gees are you sure it is just a dishwasher?

Maybe you are saying difficult to get a loop seal to protect from any drainage back into the dishwasher.

Sounds like the situation where you buy a new rubber drain hose of the proper length to allow it to be routed in a proper manner. Your hook up point might be different than the last guy, same hose isn't exactly long enough for the job.

Forget all the splicing and jury rigging. Get a hose long enough for the job. You are unclear exactly how / what the hook up point is into the drain system. Just have to fit that up as required. Normally that point is above the trap of the sink, either into the normal supplied port on a garbage disposal or to a fitting on the drain line. The drain hose is looped up high enough over that point so normal drain water from the sink can't flow back into the dishwasher.

Some local rules and regs require what is known as an air gap device be installed if the dishwasher is draining into an under sink type drain line. Some dishwashers have it built into their drain systems. Basically it is a device that installs thru the sink, it provides a drain height point above the highest level in the sink. Just web search for "dishwasher drains air gap". Used to prevent siphon flows from the dishwasher when the pump is not running.

Don't try to put air brakes on the dishwasher, definitely not required.
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Old 09-08-2009, 08:59 AM
 
Location: Visitation between Wal-Mart & Home Depot
8,307 posts, read 38,657,867 times
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Quote:
Originally Posted by beatnick fly View Post
I purchased a used Whirpool dishwasher. It has a 1" drain below narrowing to a 7/8" short flange. The sink trap also has a 7/8" fitting. I bought a rubber adapator that fits over the 7/8" flange onto the the 1" fitting of the dishwasher. (the 7/8" section of the dishwasher drain is so short a clamp will not hold it.)So now I have to connect the 7/8" section of the adaptor with the 7/8" drain hose. So I have a 1/2" nipple connecting the adaptor and the 7/8" hose. A friend mentioned this might cause an "air brake" problem. Any ideas???

If I'm reading correctly you're concerned that the 1/2" nipple connecting the sink plumbing to the DW drain line is going to create a vapor lock.

I don't think you're going to have a problem. Just make sure that you loop the drain line so that some portion of it is at least as high as the sink drain and preferably higher than the highest possible water level in the sink.

EDIT: Cosmic just barely beat me to it...
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Old 09-08-2009, 10:32 AM
 
2 posts, read 15,737 times
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Thanks everyone, I might be overthinking this, I was concerned about going from a 1" opening on the dishwasher to a 7/8" opening down to a 1/2" nipple, then back up to the 7/8" hose. Don't do a lot of (or any) dishwasher installs, never realized there were so many different types of drain lines. Going to try it anyway, if it gives me a problem, at least I'll know what it is. Thanks again.
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Old 09-08-2009, 07:07 PM
 
48,505 posts, read 96,476,720 times
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Your washer instructions on installation sholud cover everyhting including putting a loop or air gap device in the line.The wishwaher shpuld come with a hose with the fittings.
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