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Old 05-22-2022, 02:14 PM   #1
Ting3
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Dometic 320 vacuum breaker on toilet

2016 Montana high country 310re.
I've replaced the vacuum breaker on my toilet, but still have issues with the vacuum breaker sticking not allowing water into the toilet.
I've replaced both water valve and vacuum breaker on the toilet.
I can turn the water on and off on the sink next to the toilet, to bring the toilet back to life.
Any idea what might be happening!
 
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Old 05-22-2022, 02:21 PM   #2
jcurtis934
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Have been using.the domestic 320 for years with zero issues...but we also use an adjustable pressure regulator on the water line into the rv, as we note pressures from all over the range across the country. We are full timers so our toilet sees use 365. You may well be having issues if not using a true regulated device. John
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Old 05-22-2022, 04:10 PM   #3
Daryles
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I have a Thetford. The vacuum breaker on the back of the toilet has leaked twice. I replaced it the first time. Second time I plugged the top vent hole where it was leaking out. No more leaks.
Honestly I don't know why they have a vacuum breaker on a toilet bowl???
Probably some code ...
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Old 05-23-2022, 08:21 AM   #4
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I have a Thetford. The vacuum breaker on the back of the toilet has leaked twice. I replaced it the first time. Second time I plugged the top vent hole where it was leaking out. No more leaks.
Honestly I don't know why they have a vacuum breaker on a toilet bowl???
Probably some code ...
I have a 320. But I have never heard of a vacuum breaker on the toilet!! News to me!
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Old 05-23-2022, 11:31 AM   #5
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^^^^^^ Me either ^^^^^^^^
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Old 05-23-2022, 12:13 PM   #6
rohrmann
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On the 310, and I'm sure on the 320 also, there is a vacuum breaker, item H in the diagram.
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Old 05-24-2022, 06:34 AM   #7
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My Dometic 320 toilet with the seat lid removed.. This is where you WILL FIND a vacuum breaker that leads down to the toilet pedal water shutoff valve...
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Old 05-24-2022, 06:39 AM   #8
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For the OP since you have replaced both the pedal shutoff valve and backflow valve on the 320 toilet I would have to remove the line from the pedal valve going up to the backflow valve and.. with a container gently operate the pedal valve and see if water flows out of the pedal valve into the container..

If Yes then issue is a sticking or deflective backflow valve behind the toilet even though you changed it... OR.. some sort of obstruction where the backflow valve line feeds into the backside of the toilet so that water can flow out of the toilet bowl holes
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Old 05-24-2022, 08:06 AM   #9
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Originally Posted by rohrmann View Post
On the 310, and I'm sure on the 320 also, there is a vacuum breaker, item H in the diagram.
And what function does this contraption do?
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Old 05-24-2022, 05:57 PM   #10
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And what function does this contraption do?
Leak....
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Old 05-24-2022, 06:49 PM   #11
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Leak....
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Old 05-25-2022, 06:14 AM   #12
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And what function does this contraption do?
Vacuum breaker on the backside of the toilet is to prevent backflow of water from toilet into the water system ... required by code...

The one on the toliet is usually very reliable provided if you winterize you make sure this valve is either blown out or RV antifreeze used...

The anti siphon valve for the black tank flush is a complete piece of junk and should be either upgraded to an all brass one or eliminated by the owner before you have a flood in your RV
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