wrote:
"In a house that woulkd be flooded without a sump pump that depends on
electricity, where therefore a storm could really flood it, what kind
of
a generator should be bought and how much should it cost, and is that
the best precaution? "

There are backup sump pumps that are driven by city water pressure. I
would look at one of those if your main concern is just running the
sump pump. The disadvantage to a generator is that unless you get the
type that will start and transfer automatically, someone has to be
there to start it. The fully automatic systems will run a lot more
than the sump pump, but are fairly expensive.

You can set one of the backup sump pumps to kick in when the water gets
a little higher than normal on the main pump.


This is one flavor of the water-powered pump:
http://www.basepump.com/Basepump.htm

If you don't have city water, this won't do much good:-)

The other possible is a sump pump which runs on storage batteries.
They *do* require diligent care so that the batteries aren't
flat when needed most, but the cost would be far less than
an automatic generator (which may also fail when needed).

Jim