Well, lets make sure its a celenoid first..... it has bolts in it and attaches to a cord that you put a pump in.. turns off when the water gets above the doo hickey.. sound right?

This is a solenoid:

http://www.autotopoff.com/products/S/images/S01_JPG.jpg

You can pick one up at McMaster-Carr for ~$18. There are 3 versions, 24VAC, 120VAC and 12VDC. The part number for the 120VAC one is 7877K53.

Where is this Store located ? When does the solenoid kick in ?

Mcmaster-Carr is an online store. The solenoid is normally closed, so when you plug it in, the solenoid opens up (thus letting water through). I currently have mine hooked up to a float switch. If the water level in my sump gets too high, it trips the float switch and turns off the power to the solenoid, cutting off the freshwater supply.