Dr. Grow: Automatic lawn sprinklers help conserve water

An electric timer control box operates the sprinkler system.

There are many good reasons why lawn sprinkler systems are becoming more popular these days. If the automatic system is one that is designed and maintained properly, it uses water more efficiently than hand watering. The street doesn't get watered. The system turns itself on and shuts itself off at the right time, so you can play golf, go fishing, or have lunch with the girls instead of moving sprinklers and hoses around all day.

An automatic system can provide water to plants when it is best for them, which is early in the morning. Timely watering reduces plant disease and loss of water due to evaporation. You can sleep in.

If you are interested in having a system installed, what should you look for? Remember, price is not the only factor to consider. First, you need to understand the components of a system, and then see how the system is designed. Only then should you consider price.

An automatic system has a number of components. First, the system must have a water source. This source can be the potable (drinking) water system that supplies your home, or it can be a lake or a well.

If the water source is a potable water system the sprinkler prevents water from moving out of the sprinkler system back into the potable water source. For example, this backflow of water could occur if large amounts of water are used to put out a fire down the street while your system is in operation. Most municipalities allow the use of a double check valve or a reduced pressure backflow preventer. Either must be tested annually by a certified tester.

Secondly, the system has zone valves that work hand in hand with a timer. An entire lawn cannot be watered at one time. The lawn area to be watered must be broken up into zones. Only one zone can be watered at a time. When one zone is finished, the timer tells the zone valve to shut off. The timer then tells the next zone valve to open up and another zone begins to get watered.

Water is generally applied through pop-up sprinkler heads. The underground heads pop up when water pressure is applied to them. Some heads spray water. Others shoot out one or more streams of water and rotate. Each sprinkler head is rated by its precipitation rate. Precipitation rate is the number of inches of rainfall applied to the lawn area per hour. This number becomes very important in the design of the system.

All of the components are tied together through underground pipe. This is usually black poly pipe or white PVC pipe. The timer and the control valves are tied together through underground electric wire.

Now that you know the components of a system, you can evaluate a sprinkler system design. If your potential contractor won't provide you with a design then find one who will.

First, see if the sprinkler heads are evenly spaced around the perimeter of each section and throughout each section of lawn. Some cheap systems just have a line of heads running down the center of an area to be watered. A sprinkler head does not deliver the same amount of water at all distances from the head. In order to compensate for this a good sprinkler system design will have each head throwing water all the way to the next head. Each square foot of lawn will be sprinkled by two or more heads. This is the only way to ensure an even distribution of water over the entire lawn area.

Secondly, see which sprinkler heads are tied together in zones. The precipitation rates for each sprinkler head on the zone must be the same. If heads with different precipitation rates are linked together, then wet and dry spots will occur in the lawn.

If you find designs are comparable in head placement and in linkage of heads with the same precipitation rates, then look at the difference in price. You can now make a better decision on which contractor to have install your system. A properly installed and maintained automatic lawn sprinkler system can save you time, money, and be environmentally friendly by using water efficiently.

Paul Schnare of Cape Girardeau has been in the lawn and garden business for more than 20 years. He's an adjunct professor in horticulture at Southeast Missouri State University.