Originally Posted by wildtoad
So if you're at a state park with no sewer, after around 20 flushes, you are full, assuming a 40 gallon black tank and two gallons per flush to include tank and bowl. No thanks. The typical RV toilet gives the user options on how much water per flush they use.
For dry camping stays (state parks), come in with empty tanks and full fresh water, but add about 3 gal. of water in the black tank to get you started. You don't want a completely empty tank. That's when things can build up - not enough water.
When you read about using 'plenty of water' in the black tank that doesn't mean that for liquids you need to use lots of water - you could barely tap the pedal and have enough to flush liquids and clean the bowl.
You wouldn't use more than 1 gal, if that, for solids which is 'plenty of water'.
Then...before leaving the campground fill your black tank to at least 3/4 full so you'll have 'plenty of water' to dump. When dumping you want a big swish of water emptying at once. That's what cleans the bottom of the tank good.
I've never heard of using 2 gal of water with each flush.
With a 40 gal black tank we could go for two weeks of dry camping.