Black tank only for gray and black water???

[mmollema]

I am working on a 65 and have the rear bath out, there is no room for two decent size tanks. I was thinking of only doing a black tank for both types of sewage. On top of the P traps in the shower and sinks I was going to put in a horizontal check valve close to the tank. I was also going to size the waste tank larger than the capacity of my fresh water tank so I never over fill. All opinions and advice are appreciated.

[TG Twinkie]

I think you will have trouble with debris clogging the check valves. Which will cause them to leak and allow back flow into areas that you don't want.
Why not keep it simple and use 2 tanks?

[68 TWind]

My 68 has a 16 gallon black tank that is good for 4 or 5 days before it needs to be dumped. We carry an 18 gallon "blue boy" for grey water if the site has no sewer hook up. Even when we are careful with water usage we fill the 18 gallon tank in about 3 days with just sink and lav. water. You will fill the single combo black/grey tank so fast you will either have to move the trailer to dump it or use a blue boy every day or two, so why not just use a blue boy for grey water? Also, that water is mostly soapy so it is not nasty. Also, If you want to shower you will have enough tank capacity. If we stop for just one night, I put a small bucket under the rear outlet and then dump it into the toilet the next morning.
I too had the thought of combining the tanks but after 6 years of camping in our Airstream, I am very happy I did not try and combine the tanks. If I were redoing the trailer now I'd put in a grey tank but at the time VTS did not have the tanks that fit between the frame rails.

[ScottyWed]

When I had my 1960 Safari I ran into the same problem. I replaced the floor in a hurry and didn't install a grey water tank. I was able to find and install 2-13 gal tanks and tie them together. Not ideal but since my frame had a rail down the center it was the only thing I could do.

[mmollema]

The area I have to work with where the floor is removed is only 54x27x8. I cant find two tanks 27x27x8. So I figured I could get about a 40+ gallon tank and like a 35 gallon fresh water. The check valve would be above the tank and above the floor.

[USAtraveler]

I was considering doing the same thing, MM. But as Bruce points out, you will fill a single waste tank much faster, and being full of black water, the only place you can then empty it is a dump station. For my "grey" water, I collect it in a shallow bucket like Bruce does. Since it is mostly pretty clean except for a small amount of soap, you can instead empty it into the nearest sanitary sewer or toilet.

[MelGoddard]

My 2016 30' FC came with the lav sink dumping into the black tank. That means the black tank fills a lot faster that it did on my 25' FC.
The 'mothership' tells me the purpose is to fill the black tank faster to ensure that it gets properly dumped. Jeez! What are these guys drinking?
They provide a rinse circuit to ensure a cleaned out black tank, then short circuit our length of stay, while boondocking, or at a campground that doesn't have a sewer.
One of our early camps (rally) has no sewage, so do I now have to buy a 'blue boy' or some other 'goofball' tank?
Or take down the parking spot to go to the dump station?

[GiftingGirl]

I am replacing my toilet with composting toilet. No black tank needed.

[OTRA15]

Originally Posted by GiftingGirl

I am replacing my toilet with composting toilet. No black tank needed.

How do you dispose of the urine, which must be separated from the feces for the composting toilet to work?

[GiftingGirl]

Composting toilets separate the liquid and solid. There are a few great airstreamer videos on utube about how to handle. If your traveling it's campground, rest stop, gas station. I am using mine as extra unit in back yard so I will simply dump in the indoor toilet.