Most folks living in snowy cold climates don't use their outside hose bibs in the winter. However, farmers and ranchers need a year-round supply of running water for their livestock. The soil may be frozen to a depth of two feet or more, but thirsty cattle and horses still need water. A freeze-proof or frost-proof hydrant addresses this problem.
The basic unit consists of a metal standpipe, pump rod, plunger, bleed valve or check valve, lift handle, and packing nut. Frost-proof hydrants have been manufactured for decades. They are reliable, durable, and fairly easy to install.
Their operating principle is simple. The water supply they are attached to is buried beneath the frost line and remains liquid. After the hydrant is closed, any water in the standpipe drains out, and the parts of the hydrant located above the frost line are completely empty. They can't freeze shut because there isn't any water in them.
Dig a hole two feet in diameter at least one foot past the desired bury depth, which should be at least one foot below the normal frost line in your area. Attach the hydrant to the top of the standpipe and the bleeder/check valve to the bottom. Connect the water supply line. Turn on the water and check all connections for leakage. Tighten if required. Lift the handle and purge any debris or soil which may be in the standpipe. Lower the handle and visually check to see that the water in the standpipe drains properly through the bleeder or check valve. If all is in order, bury the standpipe. Fill the hole with gravel to within a few inches of the surface. This creates a frost-proof drainage area.
When the handle of the hydrant is raised, the lifting rod lowers the plunger and blocks the check valve or bleeder. The water flows out of the spout at the top of the stand pipe. Most hydrant spouts are equipped with a threaded brass male hose fitting. When the handle is lowered, it lifts the plunger and any water left in the standpipe drains out through the bleeder/check valve.
Frost-proof hydrants are manufactured by a number of companies including Woodford and Simmons. Their products are sold at many farm supply stores such as Tractor Supply. If you need advice on standpipe length, selecting the best hydrant for your needs, the frost line depth in your area or repair parts for an existing hydrant, this might be a good place to visit.