Using the Black Tank Flush Valve

Welcome to RVForums.com

  • Register now and join the discussion
  • Friendliest RV Community on the web
  • Modern site for PC's, Phones, Tablets - no 3rd party apps required
  • Ask questions, help others, review campgrounds
  • Get the most out of the RV Lifestyle
  • Invite everyone to RVForums.com and let's have fun
  • Commercial/Vendors welcome
Joined
Nov 17, 2019
Messages
787
Location
Prince William, VA
RV Year
2020
RV Make
Newmar
RV Model
Ventana 4326
RV Length
43
TOW/TOAD
2019 Jeep Cherokee Trailhawk
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?
 
Joined
Nov 2, 2019
Messages
2,116
Location
WA, MT or somewhere else!
RV Year
2018
RV Make
Newmar
RV Model
Mountain Aire 4047
RV Length
40'
TOW/TOAD
2014 Honda CR-V
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
 
Joined
Nov 14, 2019
Messages
646
Location
Orinda, CA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4002
RV Length
40’10
TOW/TOAD
2015 Jeep Trailhawk
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.
 
Joined
Jul 27, 2019
Messages
3,372
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
TOW/TOAD
2017 Chevy Colorado
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.
 
Joined
Nov 17, 2019
Messages
787
Location
Prince William, VA
RV Year
2020
RV Make
Newmar
RV Model
Ventana 4326
RV Length
43
TOW/TOAD
2019 Jeep Cherokee Trailhawk
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?
 
Joined
Jul 27, 2019
Messages
3,372
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
TOW/TOAD
2017 Chevy Colorado
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.
 
Joined
Nov 15, 2019
Messages
500
Location
DFW, TX
RV Year
2020
RV Make
Newmar
RV Model
New Aire 3543
RV Length
35
TOW/TOAD
2020 Jeep Gladiator
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.
 
Joined
Nov 2, 2019
Messages
2,116
Location
WA, MT or somewhere else!
RV Year
2018
RV Make
Newmar
RV Model
Mountain Aire 4047
RV Length
40'
TOW/TOAD
2014 Honda CR-V
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
 
Joined
Nov 15, 2019
Messages
500
Location
DFW, TX
RV Year
2020
RV Make
Newmar
RV Model
New Aire 3543
RV Length
35
TOW/TOAD
2020 Jeep Gladiator
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.
 
Joined
Jul 27, 2019
Messages
3,372
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
TOW/TOAD
2017 Chevy Colorado
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!
 
Joined
Nov 15, 2019
Messages
239
Location
SW Florida
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4369
RV Length
43
TOW/TOAD
24' Enclosed (Mini & Harley)
Each time I empty my black tank I let the internal rinse run with the gate valve open for a minute or so. Then I close the gate valve for 2 minutes, open/empty, and repeat. After these two fills and flushes I generally see clear water coming out.

With my gray I make sure I have 5 to 10 gallons of water in it on travel days. I add one or two pods of Oxy-Kem. It is amazing how much "stuff" will come out of the gray tank and how discolored the water will be when I empty it. During times when we are stationary I will close the gray every couple of weeks and add Oxy-Kem, let it sit for at least 12 hours and then empty.

We have found that odors can come from a gray tank just as fast as a black tank if not kept clean.
 
Joined
Nov 24, 2019
Messages
37
I flush my black every time I dump. I did the boiler valve mod on the outside shower valves, it's super easy to do. Then put brass quick connects on the boiler valves and the black flush connection. I keep a 3' hose to use to flush, just long enough to hang down below the wet bay door to remind me to shut it off when done because the door won't close with the hose hanging down below the opening a little. I like to use hot water, but it probably doesn't matter.
 
Joined
Jul 27, 2019
Messages
3,372
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
TOW/TOAD
2017 Chevy Colorado
I flush my black every time I dump. I did the boiler valve mod on the outside shower valves, it's super easy to do. Then put brass quick connects on the boiler valves and the black flush connection. I keep a 3' hose to use to flush, just long enough to hang down below the wet bay door to remind me to shut it off when done because the door won't close with the hose hanging down below the opening a little. I like to use hot water, but it probably doesn't matter.
This is ABSOLUTELY the key to black rinse in my opinion. When you can make the process convenient then you'll do it. I keep a flexible hose connected to the "spigot" type connections (aka boiler valves) which give better water pressure and I use a quick disconnect that remains connected to the black rinse fitting. This has been the answer to my laziness and therefore I black rinse nearly every black tank empty now.
 
Joined
Nov 2, 2019
Messages
2,116
Location
WA, MT or somewhere else!
RV Year
2018
RV Make
Newmar
RV Model
Mountain Aire 4047
RV Length
40'
TOW/TOAD
2014 Honda CR-V
I did the boiler valve mod on the outside shower valves, it's super easy to do.
I need to get busy and do this too. Haven't found exactly the right valve set yet. I'd like a mixing valve setup with hose connection rather than two separate valves. What did you use @Hawkeye?

TJ
 
Joined
Jul 27, 2019
Messages
3,372
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
TOW/TOAD
2017 Chevy Colorado
Here is what I used. One has a slightly different angle (blue) but here are options. I do not use a mixing setup as of yet, haven't had a need.



 
Joined
Nov 24, 2019
Messages
37
Hi Jim, I did Dutchstar Don's method and went to Lowes and got boiler valves. I don't have pictures, but I'm sure Don does. They are quarter turn 1/2" valves with screw flanges. It's basically plug and play, remove the existing faucet and the pex nut will screw right on to the new valves. I put small stove bolts thru the brass flange to secure them to the existing plastic base plate. The only thing I haven't done yet is to get a short Y to mix water, but at this point I have just been using one or the other and have quick connects on both. I purposely have a longer hose like I explained above, so I don't leave it hooked up or forget it on. This is a 20 minute mod, once you have the parts. Good Luck!
 
Joined
Nov 3, 2019
Messages
368
Location
Florida
RV Year
2018
RV Make
Newmar
RV Model
CanyonStar
RV Length
39' 11"
TOW/TOAD
Demco KarKaddy 460SS and VW Passat
We "flush" the black tank at least once a week when on the road, if able. I am amazed at the amount of solids that are flushed out. Not sure where this stuff accumulates but flushing especially before storage is in my opinion a good idea. Also, I keep some "clean" water in the tanks during storage to keep any residual from drying out. Luckily the storage facility we use has a dump station with water available to flush tanks.
 
Joined
Nov 3, 2019
Messages
368
Location
Florida
RV Year
2018
RV Make
Newmar
RV Model
CanyonStar
RV Length
39' 11"
TOW/TOAD
Demco KarKaddy 460SS and VW Passat
Any links for "Oxy-Chem" pods?
 
Joined
Nov 3, 2019
Messages
368
Location
Florida
RV Year
2018
RV Make
Newmar
RV Model
CanyonStar
RV Length
39' 11"
TOW/TOAD
Demco KarKaddy 460SS and VW Passat
Here is what I used. One has a slightly different angle (blue) but here are options. I do not use a mixing setup as of yet, haven't had a need.

How do you attach these valves to the existing plumbing behind the existing mixer?
 
Joined
Jul 27, 2019
Messages
3,372
Location
Midlothian, VA
RV Year
2017
RV Make
Newmar
RV Model
Ventana 4037
RV Length
40' 10"
TOW/TOAD
2017 Chevy Colorado
How do you attach these valves to the existing plumbing behind the existing mixer?
Take your wet bay shower panel off. You'll see two twist on connectors on the back. One should be marked with red tape or something, the hot line. Easiest mod you'll do.
 
Top