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Old 06-16-2020, 06:08 AM   #1
Bill-2020
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Black Flush Anti-Siphon Valve

Is there a particular reason why the black tank anti-siphon valve is placed so far up behind the sink? On ours it’s about 12-18 inches above the inlet at the wall. It is literally pushed up against the base of the faucet behind the sink. If there was a time it leaked, I would have to remove the entire cabinet, or sink bowl, to access it for repairs. If that day comes, can I cut the PEX a little shorter so that the connections can be accessed easier, or is there some height requirement above the inlet. (I would think doubtful, but I’ve seen a lot of comments on how others are tucked up behind the sink.)
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Old 06-16-2020, 06:35 AM   #2
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I’m not sure there is any rhyme or reason other than trying to get as much elevation as possible. I’ll bet there is a clamp on one of the pex lines holding it up there and if the valve fails you can remove the clamp to make repair/replacement easier. I don’t see any reason you can’t cut the pex a little shorter.
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Old 06-16-2020, 07:19 AM   #3
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This is strictly as guess on my part I would guess it's put there so that it doesn't get damaged by objects that are stored in the cabinet.
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Old 06-16-2020, 07:27 AM   #4
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Thanks Chuck. The picture I have sort of shows a potential black strap of sorts waaaay up there, looks to be connected to the faucet structure. So, if that's the case, they wanted that valve strapped to something more supportive than just the middle of another PEX line further down. I wonder if there's some movement of the valve and it's lines when the water is turned on/off. Well, wif the day comes it need some attention, I'll at least know more than I did before. And it looks like removing the sink bowl would be a better option to gain access.
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Old 06-16-2020, 07:29 AM   #5
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Originally Posted by flybouy View Post
This is strictly as guess on my part I would guess it's put there so that it doesn't get damaged by objects that are stored in the cabinet.
Good point. Let's not damage something that has nearly direct access to that particular tank!
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Old 06-16-2020, 01:16 PM   #6
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I believe that elevated position (where they bring the lines up, thru, then back down is a backflow prevention design in and of itself as sort of a safety measure for the backflow valve. I have seen bad backflow preventers just removed and then the elevated section used as the backflow prevention.
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Old 06-16-2020, 01:50 PM   #7
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I believe that elevated position (where they bring the lines up, thru, then back down is a backflow prevention design in and of itself as sort of a safety measure for the backflow valve. I have seen bad backflow preventers just removed and then the elevated section used as the backflow prevention.
That crossed my mind, but with the valve there I thought, “Naw... there’s a valve why would they make it that high.” But I see your point.
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Old 06-16-2020, 03:25 PM   #8
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Not implying that you should remove it or that it would be a good idea IMO, but I've seen it done. Thinking about it, if something happened on the water supply side that all of a sudden caused a vacuum the elevated hump would probably stop anything from being siphoned back into the fresh water supply....but, that anti siphon valve is better than an elevated section of water line IMO.
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Old 06-16-2020, 03:55 PM   #9
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If that valve went bad I’d just replace it. That would give me an excuse to caulk the sink correctly when I put it back in.
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Old 06-16-2020, 04:33 PM   #10
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I believe the anti-siphon valve needs to be higher elevation than the toilet rim. My unit has 2 black tanks and two valves...both are placed slightly higher than the toilet that drains into the respective black tank.
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Old 06-16-2020, 04:43 PM   #11
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Simple physics says if you don't have the anti siphoning valve than it can backflow if the hose connected to it is lower than the tank.
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Old 06-16-2020, 04:43 PM   #12
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Makes sense. It was explained to me at one time that it had to be higher than "something" but couldn't remember what.
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Old 06-16-2020, 04:57 PM   #13
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Just like siphoning gasoline out of a car's tank. The rubber hose goes higher then the tank in the fuel filler neck and after it's primed the gas will continue to flow as long as the hose is lower than the tank, like on the ground.
As a disclaimer... I've only used a "rubber credit card" on my own gas tank, never stole any.
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Old 06-16-2020, 06:57 PM   #14
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This is from the recpro.com website regarding these valves:

Protect Fresh Water from Pollutants 571-VAC-CHK-A

Vacuum breakers are an important part of any plumbing system connected to a toilet. This breaker protects the water supply from contamination from backflow and back siphonage. Basically put, you need one of these if you want the pipes around your toilet area to keep from being contaminated. This vacuum breaker is one that has a check valve and air vent as part of its design.

Although this piece is small and simple-looking there are several points that need to be addressed when it comes to proper water safety and installation. First, this should only be used on one fixture at a time. This keeps the pressure in the line predictable and the vacuum breaker able to handle it. Second, this vacuum breaker is a high-hazard protectant, which means that it protects the potable water supply from toxic materials. Because of this, it can be used in a low-hazard application as well. Third, it should be installed a minimum of 6 inches above the highest point of any item connected to the waste tank where the flusher is installed. This vacuum breaker should also not be under more than 12 hours of continuous water pressure. This could cause the check valve to shut or become stuck. Fourth, make sure that this vacuum breaker is installed upright. It relies on gravity to properly function and if it is installed in a different position, the valve may not fully open.
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Old 06-16-2020, 07:37 PM   #15
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Quote:
Originally Posted by bobbecky View Post
This is from the recpro.com website regarding these valves:

Protect Fresh Water from Pollutants 571-VAC-CHK-A

Vacuum breakers are an important part of any plumbing system connected to a toilet. This breaker protects the water supply from contamination from backflow and back siphonage. Basically put, you need one of these if you want the pipes around your toilet area to keep from being contaminated. This vacuum breaker is one that has a check valve and air vent as part of its design.

Although this piece is small and simple-looking there are several points that need to be addressed when it comes to proper water safety and installation. First, this should only be used on one fixture at a time. This keeps the pressure in the line predictable and the vacuum breaker able to handle it. Second, this vacuum breaker is a high-hazard protectant, which means that it protects the potable water supply from toxic materials. Because of this, it can be used in a low-hazard application as well. Third, it should be installed a minimum of 6 inches above the highest point of any item connected to the waste tank where the flusher is installed. This vacuum breaker should also not be under more than 12 hours of continuous water pressure. This could cause the check valve to shut or become stuck. Fourth, make sure that this vacuum breaker is installed upright. It relies on gravity to properly function and if it is installed in a different position, the valve may not fully open.
Well that about sums it up!! Makes sense, I just know I see them installed sideways and plumbed backwards from the factory enough times to wonder if any training is done on the assembly line.
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