Why separate black and grey tanks?

[Chuck 1935]

Why have seperate black and grey tanks ? They both get dumped down the same hole.

[Bill Adams]

Some coaches don't.
I like this option as I can drain the black and then follow that with good rinse with the grey. There are also some places that I might be able to drain grey onto the ground and just add more fresh water to extend a dry camping location. You could never do that if the tanks were combined.

[Chuck 1935]

That was my thought on dry camping exactly. Under normal conditions I might get 10 gal in the black tank and 40 in the grey. I hate to see all that capacity in the black tank going to waste IF I were to need it.
Keeping them seperate while dry camping in the desert makes good sense. Thank's

[Ernie Ekberg]

I believe Newell incorporates one tank.

[Gary RVRoamer]

And some RVs, mostly rear galley trailers, have THREE tanks. One black and two gray. This is to better accommodate the location of the sinks, shower and commode, as well as to balance the weight.

[H. Miller]

The black tank normally has a "hard" (non P-trap) type inlet for odor control. The grey has water filled P-traps which will eventually evaporate..
Imagine opening the door of your RV after a few months of storage and the black tank P-trap (if it had them) was dry!!!!!!! Something tells me that no matter how good it was "cleaned" or how much chemical was used, it wouldn't be a pleasant experience

[smlranger]

Originally Posted by Chuck 1935

That was my thought on dry camping exactly. Under normal conditions I might get 10 gal in the black tank and 40 in the grey. I hate to see all that capacity in the black tank going to waste IF I were to need it.
Keeping them seperate while dry camping in the desert makes good sense. Thank's

When we had a TT years ago, I installed a little 12v pump which allowed me to pump grey water into the black tank via the tank flush line. That would give us at least one extra day on the grey tank. No reason why you could not do that with a motorhome.

[Always-RVing]

Since grey's can fill up quickly from clothes washers, dishes, showers, etc, you can keep the grey open but not the black.

[J Walker]

I believe the separate black and gray tanks originated back when you could dump gray water anywhere but not the black water. A trick is to put the end cap on the drain, open the gray and black valves, and let them equalize. You get the gray going into the black but not vice versa.

[Ernie Ekberg]

Originally Posted by J Walker

I believe the separate black and gray tanks originated back when you could dump gray water anywhere but not the black water. A trick is to put the end cap on the drain, open the gray and black valves, and let them equalize. You get the gray going into the black but not vice versa.

Jim- if I did that to my coach- how would I get the drain hose on the outlet without getting baptized??

[Bill Adams]

Originally Posted by Ernie Ekberg

Jim- if I did that to my coach- how would I get the drain hose on the outlet without getting baptized??

You would not! Additionally, since there's no magic here, if both tanks are at the same height the black would still migrate into the grey unless you could actually watch the water flow and quickly shut things down the second that the tanks equalized.

[Gary - K7GLD]

AND, the winner IS:

Originally Posted by H. Miller

The black tank normally has a "hard" (non P-trap) type inlet for odor control. The grey has water filled P-traps which will eventually evaporate..
Imagine opening the door of your RV after a few months of storage and the black tank P-trap (if it had them) was dry!!!!!!! Something tells me that no matter how good it was "cleaned" or how much chemical was used, it wouldn't be a pleasant experience

[Ernie Ekberg]

Bill- here is my drain set up. The gray and black are separated by 4 feet. The gray drain is a 2 inch- go figure- pipe that angles down to the black drain pipe- 4 inch line valve. All the stuff comes out one outlet. And the valve is located about 4 inches upriver from the cap. Thus, and I sure ain't gonna try it, you take the cap off, to add the drain hose, and you get instant shoe cleansing.
But in the instance that this setup would have to be redisgned, the mixing of the extra gray would really help in the draining of the black tank.

[skigramp]

Instead of a using a "cap" when balancing the gray and black tanks the use of one of these will allow you to later connect the sewer hose without getting your shoes (or other body parts) wet

Look for one of these