We were fulltime RV'ers for 8 years and in out RV me had very nice johns that used less than a gallon of water to flush (maybe a little as a quart). Ours had a little petal to the side that dispensed water as long as you depressed it ... yellow liquid stuff ...zip 2 sec. The Brown stuff...zip 4-5 sec.

Seems like such a solution to water conservation I'm sure there must be SOME reson it can't be used in conventional homes...except for the fact that it ISN'T conventional.

The waste drops straight down to your holding tank. That type of thing would work if you had a collection tank under the floor and a grinder pump to move the waste down the line. The water is needed to move the waste otherwise your pipes would clog.