"Balancing" Gray Water and Black Water Holding Tanks.

[SailorDon]

In my 2014 Wilderness 2175RB, the black water tank and the gray water tank both have 35 gallon capacity.

Typically, when my Gray Water Tank is full, the Black Water Tank is 1/3 or less.
It would be nice if there was a way to pump Gray water into the unused capacity of the Black water tank.

I did a fresh water "test run" to check out a tank level balancing theory.
With both Black and Gray water tanks empty, I closed both discharge valves and placed the cap on the sewer discharge connection.
I filled up the Gray water holding tank by running the garden hose into the drain in the shower until it backed up. Gray Water gage read Full, Black Water gage read Empty.
With the sewer discharge cap still in place, I opened the Back water tank valve. Nothing happened. With the Black water tank valve still open and the cap still in place, I opened the valve to the Gray water tank. I could hear the rush of water as it transferred from Gray tank to Black tank. About a minute later, the floor of the shower had drained and both tank gages read 2/3 full.

Conclusion: With no pumps, siphons, connecting hoses, etc., it is possible by gravity flow to transfer some of the gray water into the black water tank.

Very important that you have very little black water and a whole lot of gray water for this to work. Otherwise you could end up with a very bad mixture in your gray water tank.

I would not recommend this procedure except in "emergency". Probably a good idea to have the travel trailer level.

 

[danemayer]

Hi SailorDon,

A lot depends on model/floorplan as tank positions vary quite a bit from trailer to trailer. On our trailer for example, gray #1 collects from shower and washing machine and fills first. But it's located underneath the black tank, so taking your approach would not help at all. I've thought about trying a transfer from gray #1 to gray #2, but that's also uphill and a no go.

But on a floorplan where tanks are at the same level, you probably could do as you've suggested.

 

[SailorDon]

But on a floorplan where tanks are at the same level, you probably could do as you've suggested.

I agree. Waste water tanks on different levels could get complicated, with the risk of black water entering gray water tanks.
I would not recommend gravity transfer between multiple tanks that are not on the same level.

With 2 waste water tanks, there are basically 3 tank location possibilities.

1. Gray above Black
2. Gray and Black at same level
3. Black above Gray

#3 would never work with the "emergency" gravity transfer. You could end up with black water in the gray water tank.
#1 would be almost perfect

 

[TedS]

Where are you when you want to balance gray with black? Are you in a place where you can dump or dispose of gray water?

Drain some gray into a bucket and pour it through the toilet into the black. This method would work for all tank arrangements.

 

[SailorDon]

Where are you when you want to balance gray with black? Are you in a place where you can dump or dispose of gray water?

Drain some gray into a bucket and pour it through the toilet into the black. This method would work for all tank arrangements.

If I were in a place were I could dispose of gray water, I wouldn't want to transfer it to the extra capacity of the black water tank.
I'm not planning to do a bucket brigade of gray water through my travel trailer living areas to dump it in the toilet. That is messy.

 

[LBR]

Pretty sure SailorDon posted only for informational purposes from his experience.....there was no question nor request for assistance to membership I could read.