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Old 12-28-2017, 07:27 PM   #1
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Winterizing Black Tank Flush

My first RV with a built in black tank flush.

I am assuming that the black tank flush line needs to be winterized (blown out and antifreeze) just like all the rest of the water lines?
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Old 12-28-2017, 07:32 PM   #2
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Blow it out with compressed air. It won't need antifreeze.
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Old 12-28-2017, 08:06 PM   #3
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My first RV with a built in black tank flush.

I am assuming that the black tank flush line needs to be winterized (blown out and antifreeze) just like all the rest of the water lines?
Interesting question. I winterize with antifreeze for everything but have not considered the blank tank flush line. I have no good answer. Perhaps another member can share.
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Old 12-28-2017, 08:16 PM   #4
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Interesting question. I winterize with antifreeze for everything but have not considered the blank tank flush line. I have no good answer. Perhaps another member can share.
johnbryanpeters did. Blow it out with compressed air. Works for me.
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Old 12-28-2017, 08:41 PM   #5
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johnbryanpeters did. Blow it out with compressed air. Works for me.
I now worry that I may have a costly fail...
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Old 12-28-2017, 08:45 PM   #6
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I now worry that I may have a costly fail...
It seems like water would drain down from the vacuum breaker through the nozzle into the black tank.......... but, if these flush systems have check valves on the input end as some say they do, there might be water in the line between the input connection and the vacuum breaker.
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Old 12-28-2017, 08:53 PM   #7
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It seems like water would drain down from the vacuum breaker through the nozzle into the black tank.......... but, if these flush systems have check valves on the input end as some say they do, there might be water in the line between the input connection and the vacuum breaker.
You have just brought some real cheer to my world. Springtime will tell. I always wanted to see the under side of my unit without the cover.

This specific warning/topic I have missed... I might just be the poster child for this.
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Old 12-28-2017, 09:05 PM   #8
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You have just brought some real cheer to my world. Springtime will tell. I always wanted to see the under side of my unit without the cover.

This specific warning/topic I have missed... I might just be the poster child for this.
Frankly, I don't remember blowing mine out UNTIL this time and I have had no problems.
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Old 12-28-2017, 10:32 PM   #9
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It seems like water would drain down from the vacuum breaker through the nozzle into the black tank.......... but, if these flush systems have check valves on the input end as some say they do, there might be water in the line between the input connection and the vacuum breaker.
There is no check valve on the input. The water in the input line when disconnected drains back out (due to ambient venting) and allows the seal (wafer) to close the vacuum breaker input side as the valve empties. The output side (to the tank) has a spring loaded check valve to close off the valve cavity; thus a backflow/vacuum breaker valve.
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Old 12-28-2017, 10:50 PM   #10
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There is no check valve on the input.
It's hard to say they are ALL like you say. I've seen pics on this forum of check valves in the input end although I can't say they came from all of our factories this way. Some/all could have been installed by their owners.
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Old 12-29-2017, 06:29 AM   #11
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It's hard to say they are ALL like you say. I've seen pics on this forum of check valves in the input end although I can't say they came from all of our factories this way. Some/all could have been installed by their owners.
It's true old coot's installation had an input check valve and he removed the backflow preventer/vacuum breaker valve but he is the only one I have read about. I think his install was a fluke and not per installation directives. His installation would not have allowed the valve to drain properly and if frozen would most likely have cracked. When installed, there is not supposed to be 2 check valves in series in the black tank clean out system but it happens. Personally, I think the valve is an overkill and not necessary assuming the plumbing is routed per directives (at least 6" above highest flood level rim, ie: toilet) but that is another issue. I'm done.
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Old 12-29-2017, 07:27 AM   #12
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Remember No 2 RVs are plumbed the SAME! Now the Nozzel area Can hold water/Brown,on some RVs! Just make a adapter to thread on your OS Shower and adapt to BTF inlet,when you pump A/F in sysyem hook the adapter to the BTF! Sleep Well on the Freezing Nights instead of thinking about the "Repair Bill This Spring"! Youroo!!
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Old 12-29-2017, 07:53 AM   #13
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In my R-Pod:

The lines to and from the check valve are braided flexible PVC tubing, not particularly susceptible to freezing.

The B&B Molders vac/check valve is plastic, but it'll tend to drain.

The water inlet port and the fitting attached to it are also plastic.

Edit: The water inlet does not have a check valve. From installation manual: "It is normal for trapped water between vac/check and water inlet to drain as garden hose is disconnected."

Odds of freezing and breakage are low. I would certainly not waste my time trying to get antifreeze into this subsystem.
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Old 12-29-2017, 08:26 AM   #14
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I noticed that the above list "Failed" to say Tank Nozzel is made of Plastic and Prone to Break if water stays inside! Youroo!! This Info covers ALL Members Locations,what will/Has worked for Members in "Key West might Not work well for Mi,Mn,or !
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Old 12-29-2017, 08:42 AM   #15
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Never thought about winterizing the black tank flush. This is our second winter with the trailer and no harm came to it during the first... but I will put it on my list for next winter!
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Old 12-29-2017, 08:42 AM   #16
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In my 2018 CC, the black tank flush line is braided pvc from the panel connection, to blue pex. Then blue pex runs up into my bath vanity where the check valve is located. Then blue pex from the check valve down to the black tank. Don't know what kind of fittings and tubing are down at the tank.
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Old 12-29-2017, 08:58 AM   #17
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It's true old coot's installation {maybe is was Coot's [and only Coot's] that had this... I can't remember everything and some days, I can't remember anything} had an input check valve and he removed the backflow preventer/vacuum breaker valve but he is the only one I have read about. I think his install was a fluke and not per installation directives. His installation would not have allowed the valve to drain properly and if frozen would most likely have cracked. When installed, there is not supposed to be 2 check valves in series in the black tank clean out system but it happens. Personally, I think the valve is an overkill and not necessary assuming the plumbing is routed per directives {I agree with this and I don't ever plan to run antifreeze into mine} (at least 6" above highest flood level rim, ie: toilet) but that is another issue. I'm done. {me, too}
Good day to one and all.
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Old 12-29-2017, 05:37 PM   #18
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On my Crusader everything is together including my outside hose fixture. When I pump Pink I first make sure there is Pink at the fixture outlet. I then hook it to the black tank flush connection and run it through the line. Just a suggestion to others reading this, many forget to winterize their clothes washer hookups as well. I take a large cup and open the fixture until I get Pink in both hot and cold. A simple solution for the black tank flush would also be to get a hand pump, (Harbor Freight) and adapt a hose fitting on the outlet hose and use it to force pink through the hose. Just remember it's easier to spend a little time to get it right than it is to repair it.
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