Gray water to black tank?

If all valves are closed, where would be the first place that the black tank overflowed?

The kitchen or galley tank drains separately from the other two.

Weldon wrote:
Recently went to the bathroom and the floor had about an inch of water on it.

Had 2 teenage boys with me on this trip …….


Thoughts?

Weldon wrote:
We have 2 grey tanks, one for kitchen and one for shower.

I think you answered your own question.

Had 2 teenage boys with me on this trip and they have no idea what caused the problem.


That sums it up right there.........

Quite common for lavatory sink to be plumbed to the black tank to better assure sufficient water to break down solids and force them out when drain is opened.

A lot of RVs they come together at the main dump location.

If you left the cap on and opened both valves, water will flow from the one that is more full to the one that is less full. Not a good thing when you go to drain as there will be a huge rush of water when you pull the cap off before you can get the hose on.

But as mentioned, the shower is more likely to flood before the toilet as the shower drain is lower.

We have 2 grey tanks, one for kitchen and one for shower. 2004 Montana

Our sink in the bathroom empties into our black water tank.

If they intermixed, then the shower would have been the first to overflow. But, yes, they can mix, if you left both gray and black valves open at the same time.