re: freezing pipes
19 jan 2000
>is it true that leaving the taps turned on just a drip or light stream will
>prevent the pipes from freezing even if the temp drops below 32f?
sure--50' of 1/2" copper pipe exposed to 22 f still air has about 6.5 ft^2
of surface and 10 btu/h-f of air-to-pipe thermal conductance, so at 32 f,
it loses about 100 btu/h, and a pound of water (about 10,000 drops) needs
to lose about 144 btu to freeze, so trickling 100/144 pounds of water per
hour (1.92 drops per second) through the pipe should keep it from freezing,
especially if it loses, say, another 18 btu cooling from 50 to 32 f.
but it's hard to guarantee the drip will continue with ordinary plumbing
and people, so maybe it's better to add a parallel tap or a solenoid valve
and a freezestat, or some heat tape with a thermostat, or insulate or
drain the pipes...