Water backup pumps have a float on them just like any other pump does. They
do not run all the time so there is no significant water loss.


"Tim Fischer" wrote in message
. ..
I installed a "basement watchdog" brand after a power-falure scare (water
was right up to the top of the sump when the power came back on). It
claims
that it can run continuously for 24 hours. Since my pump would never
need
to run continuously (it can clear the sump in about 30 seconds) I should
get
several days out of it.

I've never needed it for an emergency yet, but it was very cheap insurance
(about $150, installed myself). Since it's a completely separate pump, it
will also work if my main pump has mechanical failure.

The water-based backup systems weren't a good option as my sump isn't
anywhere near a water line. I also didn't like the idea of wasting all
that
good water, plus I've heard horror stories where people actually flooded
their basements with city water when a check valve failed...

-Tim