In article ,
Howard Beale wrote:

I'm not a physicist, but it also strikes me that you couldn't use the
water-driven pump to pump its own water out (along with the sump water) --
it seems like there's a perpetual motion machine there. (Cue the Simpsons
"In this house, we obey the laws of thermodynamics.")

Obviously these things work and manage to overcome some of my naive,
armchair limitations. But how?

No perpetual motion here. The ones I have used operate on a venturi
principal. Several gallons of city water passing thru and out to the
sewer (or whereever) will drag a gallon out of the sump.

You could probably implement it with a battery driving a valve from the
city supply triggered by a second float switch positioned somewhat
higher than the normal switch. Perhaps it could be done with a purely
mechanical float switch, perhaps like a toilet flush valve.

--
Rich Greenberg Marietta, GA, USA richgr atsign panix.com + 1 770 321 6507
Eastern time. N6LRT I speak for myself & my dogs only. VM'er since CP-67
Canines:Val, Red & Shasta (RIP),Red, husky Owner:Chinook-L
Atlanta Siberian Husky Rescue. www.panix.com/~richgr/ Asst Owner:Sibernet-L