Below the mister, not right below but, just off to the side you will need a solenoid switch out of the washing machine lid and some different size metal screening. It will have to be wired into the control valve for the water. When the spray comes on, it will fall on the screening and push the switch down and shut off the water at some point and when it evaporates the water will come on again. Usually some repair shops will sell the switch fairly cheep if you take it out yourself.
AND, for your Winter heater contact a plumber and have him drop off the next hot water heater at your house and then cut the water tank off and use the 40,000 BTU burner and the regulator. The tank is the only thing that goes bad on a water heater.