I have an outdoor drain set in the concrete outside the entrance to my
basement. The water table around here seems to be rising, so when we
get an extremely heavy rain water backs up from the drain (it's not
coming from the rain falling down, it's coming up from the ground).

I see he http://www.plumbingsupply.com/floodguard.html

that someone makes a one-way valve that I could probably install if I
tore up the concrete and then poured concrete to finish the
installation. But it's a lot of work so I wanted to ask others before
I started...

Anybody ever use these? Do they work okay or might they leak under
pressure?