Someone mentioned it's a good idea to install a backflow preventer on the
house sewage line.

I searched google for such product and found a few different ones of
different shapes and prices, some are called backwater preventer, some
called flood guard. I still have no idea which is the correct type.

Could someone point me to the correct type to use for a family house? I have
access to the sewage drain pipe (4-inch black plastic pipe) in the
crawlspace and would like to install myself if it's just a matter of cutting
the pipe and inserting the device.