they are all junk
dont trust them
the water operated ones are pretty wimpy,
water operated ones seem to wear out in
the controll valve switch that is triggered
when the water rises....
no one ever gives them exercise,
and you should turn them on at
least once a month to give them exercise
so when they stand dormant for a long time
the switch seems to not work or the bottom of the
controll that is in the water is totally clogged up with
silt and wont "spin" and pump out the water....
itis some sort of "venturi " type of fitting that sits down
in the water with the water hose tied into it and when the
water makes the fitting spin it pumps out the pit too....
its prretty wimpy......
I have put a few in and am not impressed
BUT
If you absolutely have to have anything
but the best I suggest you at least set it up
on a separate line going out of the house.....
DO NOT tie itinto the regular sump line becsuse sometimes the
head pressure is too great for it to overcome and
actually pump water out of the house....depending on what
is going on outside at the other end of the pipe......
just put another pipe out the side of your house
for the emergency back up pump
look at this one, its the best
http://www.zoeller.com/zcopump/products/backupsystems/aquanot.htm