why separate tanks for grey and black water?

TexasShadow wrote:
none other than practical.
gray water can be dumped, sometime, at some places, on the ground, legally, where black water must always be dumped in a legal sewer receptacle.
so sometimes, you can extend your stay at a campground without moving your rig.

This is interesting that it's been mentioned so many times. I've literally never camped in a campground that allowed this.

BB_TX wrote:
There has been a couple occasions when I forgot to check the grey tank level. Backed up into the shower while I was in there. Found myself standing in an inch or two of water. Glad it was grey and not a mix of black.

This alone would be a reason for 2 tanks. This happens to us quite often that we let a tank backup before I go empty them. Having poo-flavored water in any sink or shower would gross me out.

Randu wrote:
Much easier to store and handle a sewer hose that has been flushed out with gray water than one with black.
Randu

If I use a black tank flush, I don't worry about doing gray last for my sewer hoses. By the time that I am done, it's flushing clear water through which is better than the stinky gray tank any way. But, I only have dumped at my full hookup site where I didn't have to worry about time or a line behind me. If dumping at the campground's dump station is a regular thing, this might not be something that you can bank on as much.