Our tank nipple kits are made of schedule 40
galvanized pipe with 4" of thread on one end.  
They are
used for mounting the Watson float valve to the bottom of the
stock tank.  Can be used in steel, fiberglass, and poly tanks.  
Use the tank nipple in the bottom of a tire tank when using a
fiberglass or steel plate bottom.
They can also be used for
overflowing into additional holding tanks by mounting on
the side of a tank.