Low power, low pressure pumps circulate liquid in closed loop heating pipes. Hot water from solar water panel, wood stove or propane water heaters can be used to heat floors, radiators, and even circulate water under water beds and compost toilets. 1/2" threaded fittings.Use several small pumps, one for each zone rather than zone valves and a bigger pump. DC circulating pumps use much less power than AC pumps, just 18 to 50 watts. These can be powered from batteries, or direct from a solar ...