Frostproof hydrants are basically faucets, although they may differ
somewhat in design from ordinary faucets.
Two important features of a frostproof hydrant are: (1) The valve is
installed under ground--below the frostline--to prevent freezing, and
(2) the valve is designed to drain the water from the hydrant when the
valve is closed.
Figure 3 shows one type of frostproof hydrant. It works as follows:
When the handle is raised, the piston rises, opening the valve. Water
flows from the supply pipe into the cylinder, up through the riser,
and out the spout. When the handle is pushed down, the piston goes
down, closing the valve and stopping the flow of water. Water left in
the hydrant flows out the drain tube into a small gravel-filled dry
well or drain pit.
[Illustration: _Figure 4._--Vacuum breaker arrangement for outside hose
hydrant.]
As with ordinary faucets, leakage will probably be the most common
trouble encountered with frostproof hydrants. Worn packing, gaskets,
and washers can cause leakage. Disassemble the hydrant as necessary to
replace or repair these and other parts.
Frostproof yard hydrants having buried drains can be health hazards.
The vacuum created by water flowing from the hydrant may draw in
contaminated water standing above the hydrant drain level. Such
hydrants should be used only where positive drainage can be provided.
Frostproof wall hydrants (fig. 4) are the preferred type. For servicing
sprayers using hazardous chemicals, hydrants having backflow protection
should be used (fig. 5).