Last year I purchased a Coleman 'Hot Water on Demand' system since we camp at the shows so I want a hot shower and, if it is cold, I want one for the horses too. At home they have an installed hot water tank so I think that is only fair <G>.
Anyway, the Coleman unit can be either set up to syphon from a bucket or connect to a garden hose (you have to by the hose connection separately, if I remember). Anyway, you are only limited by the size of the portable propane tanks. It uses the small green ones that are around 4" in diameter and about 7" high, and they last for quite a while. The water can get VERY hot....you can make tea from the hotest setting, but the controls are very accurate when setting the temperature. The pump, on this unit, runs from a plug-in rechargable battery that lasts and lasts.
We were at Walnut Hill for 6 days and two of us took showers each day and washed long hair several times and still only needed a new tank the last day. I guess we used a tall bucket of water for each shower. We didn't bath horses with it this trip but, hopefully, you can guess-ta-mate the amount of propane tanks you would need....you will have to do a websearch to check, but perhaps you can connect the unit to a larger propane tank for around the barn.
The whole unit comes in a nifty carrying case that holds several propane bottles as well....makes it neat for traveling and storage. I have had a Zodi brand shower before and like this unit MUCH better. I do know people who have the Hott Water unit and like it very much, but look for a hose or syphon attachment, much better than a water storage unit.
And, in case you want to know how we shower <G>...I hang a hoola-hoop from the ceiling of the trailer, hang 2 shower curtains from that and stand in a big muck tub to catch the run-off....if the floor of our trailer drained away, I guess you wouldn't need the muck tub, just a bath mat to stand on to keep your feet clean.
