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Using the Black Tank Flush Valve

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MapNerd

RVF 1K Club
Joined
Nov 17, 2019
Messages
2,298
Location
Prince William, VA
RV Year
2020
RV Make
Newmar
RV Model
Ventana 4326
RV Length
43
TOW/TOAD
2020 Ford F-150
Fulltimer
Yes
Time to give the sewage tank a rinse. I haven’t done this yet, and sensors aren’t fouled or anything but I figured I should probably do it one a month at least. Anyway, before hooking up wanted to know if I need to add a Backflow preventer or if anyone knows if one is already built in. I can’t tell from looking behind the panel if there is one or not.

Planned to just hook up to my hose spigot Y, then to the black tank flush valve, open the gates and let it flow. Am I doing this right?
 
There's already a backflow preventer in the tank rinse system. It is required by code. If you want to add a second backflow preventer at the spigot, it won't hurt anything, but it is unnecessary.

Your suggested procedure is fine. We alternately close and reopen the black tank gate valve when flushing to get a full rinse of the tank bottom. If you do this, be sure not to leave the gate valve closed for more than a minute or two. You don't want to walk away and forget you have water going into the black tank with the gate valve closed. Bad things will happen if the black tank gets filled and there's water still going in.

TJ
 
I flush mine a couple of times like TJ suggested above...Not more than 1 to 2 min max (set the timer on your watch or phone) with the valve closed and when I see clear water coming out, I am done.
 
I have a SeeLevel tank monitor at the wet bay so I can see the tank levels so I will first leave black open and run the rinse. Then I'll close the black valve and let black fill maybe up to 50% then open black and let the higher flow clean out again. Once complete then do grey. Flush black as often as you have time to do it, i.e. each black tank dump if you can. I started out doing it less frequently but this is one of those things where I don't want negligence to catch up with me. I also frequently use and vary between Dish soap in the black tank, Happy Camper extreme cleaner (put some in, fill with water, drive to next CG then dump), Cascade and of course the routine happy camper odor preventer but honestly doubt it's effective. Nothing is going to handle that much odor!! I've even done the ice cube tray dump prior to travels. I have to give all the myths a try :) I think dish soap and cascade are important to do regularly to both tanks.
 
Thanks all. I added a check valve to the rinse hose anyway as I found one I had lying around. I’ll probably get more rigorous about rinsing it as well.

@Neal how are you adding all that stuff to your tank, just down the toilet?
 
I also have a check valve at the rinse connection but as I had to replace the ones under the half bath sink I learned they have the check valve inline. Theirs is quite cheap just plastic stuff. I installed brass ones. I was chasing an odor problem.

Half bath toilet is where I add the cleaners. Mine is gravity drop but that shouldn’t matter. I also try to add water to the tank prior to the dump such as flush multiple times do it’s not just body stuff but higher water proportions.
 
Don’t forget to treat the gray tank, too. I also use the liquid Cascade down the kitchen sink, and shower. Soap scum, hair, and food particles/grease (even wiping dishes & pots into the garbage first), will begin to cause false readings on the gray as well. I back flush mine every time I dump if I’m at a full hook up park.
 
So, how are folks "rinsing" or "back-flushing" gray water tanks. To my knowledge, the provided tank rinse connection in the wet bay only works in the black tank. Have I missed something?

We do put some dish soap into both the gray- and black-water tanks when we head down the road, and dump them at our next destination.

TJ
 
Ok, I’m not sure on the Newmars, as I don’t have mine yet. On my current coach, I back flush via one of these.


The black and gray lines come together in a wye just before exit...I close the gray valve, and back flush the black tank with this gadget. I time the water going into the tank, so it’s about 3/4 full, cut off the water, and dump the tank. Repeat if the water‘s not running clear. Then do the opposite with the gray tank...close the black valve, back flush a couple of times. Harder to see when the gray tank’s clean.
 
So, how are folks "rinsing" or "back-flushing" gray water tanks. To my knowledge, the provided tank rinse connection in the wet bay only works in the black tank. Have I missed something?

There is no gray tank rinse nor do I think it's needed. I do have concern about soaps returning to solids and as we know soap is very hard to break down which is why I think the dish soap and cascade is important to add which I do through the sinks. I will sometimes put happy camper in the sink too, after using the barker tank for two months I can tell you the "gray matter" stinks too!
 

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