The control valves regulate the flow of water through your entire irrigation
system, from the main water source all the way to the sprinkler heads.
They may or may not be connected to an automatic timer. If connected,
they are opened and closed by the timer. Otherwise they can be turned
off and on manually. Generally, only part of the lawn is watered at a
time so that there is not a decrease in water pressure. To keep the water
pressure rate constant, several valves may be used, with only a few sprinkler
heads connected to each one. Most homes have several valves designated
for the front lawn and several others designated for the back.
to look for
Each valve should have an antisiphon device to prevent water from backing
up into your house water supply. Separate valves should be used to regulate
water flow to areas of your yard with different water requirements.