In an irrigation system, there are two basic types of valves: shut-off valves and sprinkler valves. Shut-off valves (?EUR??,,????'??gate valves?EUR??,,????'?? or ?EUR??,,????'??ball valves?EUR??,,????'??) are used in a continuous pressure main line to temporarily turn the water off to the entire system or a section of the system. Sprinkler valves (manual or automatic) are used to deliver the water from the continuous pressure main line to the sprinklers. When the term ?EUR??,,????'??valve?EUR??,,????'?? is used alone, it usually refers to an automatic control valve. Gate valves have a wheel type handle, and several turns of the handle are required to turn off the flow of water. Gate valves are most commonly used on mainline pipes with high water pressure or high water flow. Because several turns are required, they are easier to turn off and the potential for damage caused by water hammer is reduced. Gate valves have a brass-to-brass seat, which means that they may eventually lose their secure seal. For this reason, gate valves are not recommended for frequent use. Ball valves have a single arm or lever that requires one-quarter turn to turn on or off. This single action is convenient, but caution should be used and the valve should not be turned on or off too quickly, because damage to the system from water hammer could result. Ball valves have resilient seats that keep a seal longer than brass-to-brass seats, making ball valves a better choice than gate valves where frequent use is expected. Among sprinkler valves, manual control valves are not as common as they once were. The manually controlled sprinkler system requires an operator to time the irrigation of each zone, and to turn valves on and off at the proper time. The operator must be present the entire time the system is operating. Obviously, this type of system does not have the convenience of the automatic system. Automatic control valves are used in conjunction with automatic controllers or timers, and are a much more convenient way to deliver water to the turf. Because these valves can be more precisely controlled, an automatic system allows the sports turf manager to efficiently schedule the delivery of the right amount of water to each zone. There are many types of automatic control valves. On systems not connected directly to city water systems, choose a valve with an inexpensive self-cleaning filtering mechanism. Because of the possibility of higher surge pressure in a large turf system, it is recommended that the valve be able to withstand pressures up to 200 psi. A pressure regulator can be installed at the beginning of the system, but with the long main line and the potential for high friction loss, it is generally better to have an automatic control valve with a built-in pressure regulator and control the pressure right at the valve. Placement of the valves should be planned with maintenance and safety in mind. Automatic control valves are generally installed in groups, or manifolds, and placed underground in a plastic or concrete valve box. If the valves will be near the field of play, use plastic. The manifolds should be built with plenty of room between valves. The distance between valves is dependent on the size of the valve box; for most standard size boxes, two or three 1?EUR??,,????'?? valves can be installed in a valve box, while valves larger than 1?EUR??,,????'?? are usually installed one valve per box.