hi Glenn,
Glad to see you're back among the living. Or what passes for such around here.
My thought was to hook up the "cold" water inlet to the "hot" water supply line which is, as I wrote, 30 feet or so from the hot water tank.
Since the dishwashers and washer fill by volume not time or flow rate, it wouldn't be all that important whether they were getting a strong flow or just a little stream.
And, should someone decide to run three or all four at once (possible, in my family it is standard to do exactly the opposite of what I request just to "prove" to me that I am an unwelcome idiot who doesn't know jack) then those 30 feet of "cooled" hot water would be cleared out of the system right quick and the load would be determined by only raising the water 30°F or so.
My tankless electric heater fills the bathtup very fast and runs at, oh, hell, 3-phase, never mind, must never mind.
Thanks again to all for the advice and help.
panthera