Just a curious idea. We are camping without sewer for the next 5 days, Our black tank will hold just fine but the grey tank for the shower will be an issue. We have 2 grey tanks 1 for shower and bath sink and the other is the kitchen and outdoor kitchen. Here is my question. Both tanks have their own dump valve, both tanks are at the same height on the frame. And both tanks merge into the same pvc sewer pipe to exit the camper. My Question is could I buy one of those gate valves that lock on to the end of the trailer sewer connection, close it and open the 2 dump valves on the grey tanks?My theory is that both tanks would fill at the same time essentially doubling my shower water capacity, Kind of like a water level.This seems to me like a great simple idea which probably means I am missing something. Thanks for any advise

It would work since water seeks it's own level.

That will work, just remember to CLOSE BOTH Grey Tank valves before opening the Black tank valve once the hose is hooked-up. This way you'll still have the grey water to flush the hose after dumping the black tank.

Sounds plausible. When I was being told how to use my Sani Con system, the dealer said I should empty the black tank then turn off the Sani Con and open the grey water to let it flush back into the black tank, then close the grey and continue to dump the black. You would be doing pretty much the same thing.

I accomplished it by using this, install it closed and the pull both grey tank levers tanks will equalize. See linkClick here

I glued one of those valves to the output, now share gray tanks with no problems

Merging grey tanks, is it possible? | Good Sam Community

the_bear_II
Explorer
Nov 25, 2015
It would work since water seeks it's own level.
We_Cant_Wait
Explorer
Nov 25, 2015
That will work, just remember to CLOSE BOTH Grey Tank valves before opening the Black tank valve once the hose is hooked-up. This way you'll still have the grey water to flush the hose after dumping the black tank.
bdpreece
Explorer II
Nov 25, 2015
Sounds plausible. When I was being told how to use my Sani Con system, the dealer said I should empty the black tank then turn off the Sani Con and open the grey water to let it flush back into the black tank, then close the grey and continue to dump the black. You would be doing pretty much the same thing.
bg71361
Explorer
Nov 25, 2015
I accomplished it by using this, install it closed and the pull both grey tank levers tanks will equalize. See link

Click here
JesLookin
Explorer
Nov 25, 2015
I glued one of those valves to the output, now share gray tanks with no problems
Hvyhauler
Explorer
Nov 25, 2015
It works for me... I've used this procedure before.I use a Valtera part # T58 twist on 3" waste valve (aka gate valve) and keep it capped on the end until dumping time.

As others have said don't open the black tank valve while using this process.
TucsonJim
Explorer II
Nov 25, 2015
Another nice feature of having the Valterra valve on the dump outlet is that if any of your tank valves have a leak, you won't get a nasty shower when you pull the cap off to dump. BTW, I use one the valve to equalize our tanks too.
Old-Biscuit
Explorer III
Nov 25, 2015
I installed an 'extra' valve on main drain header that all three tanks use.
With it closed I open both grey tank drain valves equalizing them. 50 grey and 28 galley for total of 78 grey

And with it closed I can even open black tank and equalize all three tanks for 128 gallons total capacity.

Yes black and grey combined.........it's all waste water and grey can stink worst then black
Was a time RVs had just one tank. Waste is waste and gets dumped into same place.
rhagfo
Explorer III
Nov 25, 2015
I going just ask how many using the shower?? DW and I have gone 8 days on out Grey tank. It is just a matter of using water conservation. That was with both of us taking daily showers.
omextreme
Explorer
Nov 25, 2015
rhagfo wrote:
I going just ask how many using the shower?? DW and I have gone 8 days on out Grey tank. It is just a matter of using water conservation. That was with both of us taking daily showers.

4 showering. 2 - 5 yr old boys that like the dirt.

We may be fine but this will be the first longer test of the new trailer and we are not sure how much water we are using yet....