How Much do Automatic Sprinkler Systems Cost? Part IV
Do you need anti-siphon valves?
There are two basic types of valves: inline and anti-siphon. An inline valve is the most common type of valve and when it is used on a municipal water supply you must install some type of backflow prevention further up the line from it. Anti-siphon valves serve the function of a backflow prevention device and, although an anti-siphon valve typically costs more than an inline valve, it saves money on the installation by eliminating the need for a system backflow prevention device and a valve box (anti-siphon valves have to be above ground or they won’t work). Anti-siphon valves are most common in California.
Most of the valves in a sprinkler system are used to control the flow of water to a specific area of “zone” within the yard. The automatic sprinkler timer sends electric current to these valves to open them. In a typical residential sprinkler system only one control valve is on at any one time so that there is plenty of water pressure for the zone. Some cities recommend or require the installation of an automatic “master” valve in front of the control valves. At the start of each cycle the master valve opens and allows water to flow as the control valve for each zone opens. At the end of the cycle the master valve closes. This helps ensure that water will not be wasted in the unfortunate event that there is a leak on one of the control valves. A master valve will increase the price of your system by one valve and associated fittings and wire. It also requires that you select at least a mid-level sprinkler timer.
Do you need spray heads in medium or large-size areas?
Any area greater than 30 feet by 30 feet is typically regarded as a medium area. While spray heads can theoretically be used to water any size area, if the area is greater than 30 by 30 then spray heads are probably going to cost more than gear drive sprinklers or “rotors”. Even though rotors are cheaper to install for medium and large areas, some homeowners simply prefer having all areas in the front yard – whether small, medium or large – watered the same way. The latest technology on the market, called “spiral rotators” or “multi-stream rotators” have the advantage of providing uniform appearance and consistent water application across all areas large and small, but unfortunately installation cost for spiral rotators is still almost as much as medium area rotor, making them an expensive alternative for small areas.
Do you need pressure regulating spray heads?
Some cities require pressure regulating spray heads in order to reduce the amount of “misting” and water waste from spray nozzles and to compensate for poor irrigation designs by making sure that all nozzles in a zone operate at the same pressure regardless of design. The cost of a pressure regulating spray head is typically 3 times that of a standard spray head. If you can afford them, it is a good idea to install them. One of the latest trends in some markets is to use 6 inch high spray heads instead of 4 inch spray heads, which allows for today’s longer grass cutting lengths and still keeps the nozzle spray above the grass. However, the cost of a 6 inch pressure regulating spray head, which is the “Cadillac” of spray heads, is more than 6 times a standard spray head. But it is probably outside the budget of the average homeowner.