I was having a cold one with a camping buddy of mine and we were talking about the fun subject of black tanks.It got us "thinking" what if one was to place a DC pump that pumped grey water into the black tank. The purpose of this would be to help rinse the black tank out, and to allow this process to be done while boondocking.I know typical RV'ing dictates that grey/blackwater be dumped into specific spots, however, sometimes we go "insanely" out there.... Where a highway turns into a gravel farm road.... For miles and miles. Then turns into two tire tracks for miles and miles. Then the tire tracks vanish and there is desert and rocks (West Texas). Out here we don't use toilet chems either (for environmental reasons). So rinsing is nice, but freshwater is lean when boondocking.Anyway, are there any setbacks, considerations, etc., to having a pump from grey to black?I was considering doing this on my bounder. I'll leave my class C in tact as that Toyota has shower & black tank together anyway.

no need to pump it... just open the grey valve first... then the black valve... and it will seek its own level, done it many times. grey tank always fills up way before black. OH YEA... make sure to keep the outside valve closed :S

A macerator pump would be a better solution it could be used on grey or the black to break up any pieces while pumping.

There is a member on the Sportsmobile forums who did exactly this. He put two check valves (one on the grey water tank, one on the black, so it couldn't go back into the grey), attached a pump, and when his GW tank is looking full, he presses a button and water gets moved to the black tank.There is always the manual method of a five gallon bucket and moving grey water to the toilet that way.

I installed a gray tank to black tank transfer pump on my 95 Bounder, over 10 years ago. Seeing how I have 100 gallons of fresh water and 2 50 gallon waste tanks, it allows me to use all my fresh water when boon docking and help flush out the black tank when dumping. I used a Little Giant magnetic drive acid pump that needs no shaft seal. The pump discharges into the black tank vent stack. No back flow possible. It is also set up to pump the gray water to a garden hose, if necessary.Richard

Like BadBoy my tanks are on the same level and the two valves are less than 12" apart. Open the grey first and then black and you can hear when there is not any more flow. On the one outlet I have a cap with a hose valve on it so when ready to hookup the dump hose I open this valve and drain the contents into the dump hose before taking the cap off. Works well and the cap and valve cost less than $10.

Pump grey tank into black tank? | Good Sam Community

badboy368
Explorer
Mar 28, 2014
no need to pump it... just open the grey valve first... then the black valve... and it will seek its own level, done it many times. grey tank always fills up way before black. OH YEA... make sure to keep the outside valve closed :S
the_bear_II
Explorer
Mar 28, 2014
A macerator pump would be a better solution it could be used on grey or the black to break up any pieces while pumping.
mlts22
Explorer
Mar 28, 2014
There is a member on the Sportsmobile forums who did exactly this. He put two check valves (one on the grey water tank, one on the black, so it couldn't go back into the grey), attached a pump, and when his GW tank is looking full, he presses a button and water gets moved to the black tank.

There is always the manual method of a five gallon bucket and moving grey water to the toilet that way.
RLS7201
Explorer II
Mar 28, 2014
I installed a gray tank to black tank transfer pump on my 95 Bounder, over 10 years ago. Seeing how I have 100 gallons of fresh water and 2 50 gallon waste tanks, it allows me to use all my fresh water when boon docking and help flush out the black tank when dumping. I used a Little Giant magnetic drive acid pump that needs no shaft seal. The pump discharges into the black tank vent stack. No back flow possible. It is also set up to pump the gray water to a garden hose, if necessary.

Richard
Ivylog
Explorer III
Mar 28, 2014
Like BadBoy my tanks are on the same level and the two valves are less than 12" apart. Open the grey first and then black and you can hear when there is not any more flow. On the one outlet I have a cap with a hose valve on it so when ready to hookup the dump hose I open this valve and drain the contents into the dump hose before taking the cap off. Works well and the cap and valve cost less than $10.
Dutch_12078
Explorer II
Mar 28, 2014
I installed a third waste valve on the outlet of my coach. After draining the black tank with both the third valve and the black valve open, I close the third valve and open the grey valve. The grey water then seeks it's own level in both tanks, giving the black tank a rinse. After it sits for a few minutes, I then open the third valve again, draining everything. My external tank level sensors don't normally have any problem reading the levels like the internal sensors do, but too much crud build up can effect them anyway.
Old-Biscuit
Explorer III
Mar 28, 2014
I installed another dump valve on the main drain line just before the outlet.

With it closed I can open all three waste tanks (black, grey, galley) tying them all together. Open just the grey & galley tying them together. Open black & galley tying them together. Open black & grey, tying them together.

Lots of options with just adding one other valve. No pump, no power draw.
OnaQuest
Explorer
Mar 28, 2014
RLS7201 wrote:
I installed a gray tank to black tank transfer pump on my 95 Bounder, over 10 years ago. Seeing how I have 100 gallons of fresh water and 2 50 gallon waste tanks, it allows me to use all my fresh water when boon docking and help flush out the black tank when dumping. I used a Little Giant magnetic drive acid pump that needs no shaft seal. The pump discharges into the black tank vent stack. No back flow possible. It is also set up to pump the gray water to a garden hose, if necessary.
Richard

Richard, I like your idea much better than letting the tanks flow together at any time.

Since I saw yours last spring, I have assembled the parts and will install it all while in Illinois this summer.
Roadpilot
Explorer
Mar 28, 2014
On our MH there is a connection between the gray and the black at the top of the tank with a check valve. The gray can go into the black but not the reverse. The gray overflows into the black.
DSDP_Don
Explorer
Mar 28, 2014
My coach and many of the Monaco's have the SaniCon macerator installed. This system hooks a hose from the main drain connection to the macerator and grinds ALL waste, both grey and black. With both tanks mounted at the same level, you can easily open the grey and pressure will make it equalize with the black. This can be done in an emergency where you need more grey space.

When I'm dumping while on the road, I routinely dump my black tank, open both valves and let the grey fill the black. I do this a 2-3 times. It works well and you don't even need fresh water to dump. On the SaniCon system, once you've dumped the last of the grey, you just put the cap on the end of the hose and put it away. No rinsing necessary.

Another advantage of doing this.....your grey water is generally soapy from showers and dishes. Allowing it to fill the black tank washes and lubes the black tank.

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