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Old 05-29-2011, 08:49 AM   #1
albertr
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Leaking check valve on Black water flush

A new problem. If it ain't one thing it's another. Back flush started leaking like crazy. Just pulled it apart. Not an easy job. There is a check valve of sorts in the line in the wall between the shower and the sliding door. Removed the shower faucets and pulled the loop down so it could be see, THe whole top is gone off the plastic valve. Is there a better valve than the original? It was never touched. Just kinda broke apart. THanks...Al
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Old 05-29-2011, 01:23 PM   #2
therink
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Just wondering; is there a possibility it may not have been purged of water when winterizing and maybe cracked when frozen? Just a thought. I blew mine out with compressed air before winter. Haven't tried it yet though.
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Old 05-29-2011, 07:07 PM   #3
hankaye
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albertr, Howdy;


Quote:
Originally Posted by albertr View Post
A new problem. If it ain't one thing it's another. Back flush started leaking like crazy. Just pulled it apart. Not an easy job. There is a check valve of sorts in the line in the wall between the shower and the sliding door. Removed the shower faucets and pulled the loop down so it could be see, THe whole top is gone off the plastic valve. Is there a better valve than the original? It was never touched. Just kinda broke apart. THanks...Al
Know what ya mean.
Posted this a few days ago.


http://www.keystonerv.org/forums/showthread.php?t=2832

Shouldn't have had any water in it as it also has a vacuum breaker built into it. That allows all the water to drain into the black tank.

Thinking about just using an elbow (pex to pex maybe $3.00), to replace the m-i-c-k-e-y m-o-u-s-e over priced valve. I believe the vacuum breaker function of it allows sewer gass to escape into that compartment it lived in. The hose connection in the exterior wall should have a check valve in it as the same valve is used for the city water inlet.

hankaye
I plan on disableing that checkvalve and buying a backflow preventer at the local hardware store (about $5.00), screw it onto the end of the hose (either end), and as the magician sez ZOOT-ZOOT POOF ... VOLIA!
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Old 05-30-2011, 06:50 AM   #4
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Howdy All;

Allow me to clarify something I wrote in my previous post.

"Thinking about just using an elbow (pex to pex maybe $3.00), to replace the m-i-c-k-e-y m-o-u-s-e over priced valve. I believe the vacuum breaker function of it allows sewer gass to escape into that compartment it lived in. The hose connection in the exterior wall should have a check valve in it as the same valve is used for the city water inlet."

The last sentence SHOULD have read;

The hose connection in the exterior wall should have a check valve in it as it is the same AS THE ONE used for the city water inlet.


My BAD

hankaye
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Old 06-01-2011, 06:02 AM   #5
Eckerhill
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The valve is very susceptible to freezing and a MT dealer told me a year or so ago that he sold a lot of them at this time of year. A special hand pump device is sold to be able to slowly add antifreeze into valve so it won't freeze.
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Old 06-01-2011, 06:51 AM   #6
therink
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I used mine the other day after hard winter and it didn't leak. Yay! I blew the flush line out with air last fall when winterizing it.
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Old 06-01-2011, 07:38 AM   #7
hankaye
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Howdy All;

Did my fix yesterday. posted it down in;

http://www.keystonerv.org/forums/showthread.php?t=2832

Contrary to what I thought, the inlet valve does NOT have a check-valve in it. Therefore there is no reason why the cheap piece o-cr*p they put in the system should freeze and bust. Unless, of course it's designed to do so..... or is mounted in such a way for it to hold water.....

Just my honest Opinion...

hankaye
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Old 07-27-2019, 11:54 AM   #8
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Hello All; Just got a new-to-me 2016 Passport 2510RB, tried the black water flush and had water gushing out into the cabinet under the sink in the bathroom. Trouble-shooting found the vacuum breaker "B&B model 571" leaking spewing water out the top i.e. value would not close as designed and divert water to the outlet. Started looking at the system...once you disconnect the hose on the outside of the unit, the line is exposed to atmosphere...there should be no vacuum or residual pressure in the line...Why do I need this value which I read is prone to fail and leak????
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Old 07-27-2019, 12:08 PM   #9
chuckster57
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The valve is an anti siphon valve meaning it prevents liquid from flowing back from the tank.

While I see your side of the question, and yes the valve is located higher than both the connection and the tank, it is required to be there. Odds are the “dirty” water will never flow back into the fresh water but as long as there is a chance, all measures to prevent it must be taken.

Many members have replaced it with a brass one from a local big box hardware store.
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Old 07-29-2019, 06:43 PM   #10
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Could it be that your backflow valve is installed backwards?
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Old 07-29-2019, 07:44 PM   #11
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Quote:
Originally Posted by hankaye View Post
Howdy All;

Allow me to clarify something I wrote in my previous post.

"Thinking about just using an elbow (pex to pex maybe $3.00), to replace the m-i-c-k-e-y m-o-u-s-e over priced valve. I believe the vacuum breaker function of it allows sewer gass to escape into that compartment it lived in. The hose connection in the exterior wall should have a check valve in it as the same valve is used for the city water inlet."

The last sentence SHOULD have read;

The hose connection in the exterior wall should have a check valve in it as it is the same AS THE ONE used for the city water inlet.


My BAD

hankaye
We have used our black tank flush system almost weekly since we started full time in late 2012, and the vacuum breaker/back flow valve is still working great. We have never had it exposed to freezing temps, so that has never been an issue either. Our tank flush hose connection does NOT have a check valve in it, so when done do the flush operation, the water from the back flow valve drains out the hose connection and the water on the tank side of the valve drains into the black tank, so there shouldn't be any water in the line, except for a low spot in the line near the tank. Our back flow valve is between the shower wall and the back of the pantry cabinet in our rig, so, if needed, access would be through a hole cut into the pantry cabinet wall.
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Old 07-30-2019, 04:03 AM   #12
Scanner
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Hey Joey;
Actually I checked everything. The flow indicator on the value agreed with how it was installed.

I understand completely the need to keep liquid from flowing backwards into the freshwater system. However, on my unit the black water flush is a DEDICATED connection...the external connection for the hose runs directly to the black water tank (and the sprays). There is no chance of "siphon" action causing liquid in the tank from being drawn up the connection hose to the fresh water system.
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Old 07-30-2019, 05:23 AM   #13
drew999999
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I've also wondered why there is a check valve for the black tank flush since its an isolated system from the fresh water. Then I realized it's more than likely for vapor and/or splash control. If you were to put in an elbow, the possibility exists for the goop in the tank to potentially splash side to side when towing down the road and fill the flush line with back pressured nasties and spill out of the inlet. I thought about this after filling my fresh water tank and heading out to the campground. I'd see some spill over from the vent when going around corners once in awhile. I'd also think that an unchecked line would also allow some level of smell to escape. My flush inlet is in the same compartment as my fresh water inlet, so this would lead to a potentially unsanitary situation.
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Old 07-30-2019, 07:10 AM   #14
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Drew, You're correct in your description of what "could happen". Another potential is a plugged vent stack. If the black tank is full AND the vent stack is plugged, the black tank flush line could become a "alternate vent" for the tank. If the tank were being used in a cool environment, then towed to a hot environment (think high altitude dry camping where the temps are cooler than the valley), there's a chance that as the contents warm up, with no vent to take the increasing pressure, the black tank flush could become the vent and push liquid out of the side connection on the trailer. With the anti-siphon valve missing, it could flow into the vanity or the wall behind the shower. With a "straight connector" installed in place of the anti-siphon valve, it could flow out of the trailer sidewall connector.

So, there's more than "just sloshing" that could occur. Even though it's not a "robust, durable" anti-siphon valve, it is a necessary part of the black tank flush. Replacing it with a HD anti-siphon valve or a check valve is the safest way to protect both your trailer systems and the fresh water system/environment from "yecht".........
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Old 07-31-2019, 09:31 AM   #15
WPWilson
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Mine was plumbed backwards. I replaced it with an elbow. NO MO PROBLEM!!!
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