In the following series of photo's and narratives, we
will show you how to evaluate your home sprinkler system. This evaluation
will allow you to make more informed decisions on when and how long to
allow your sprinkler to operate to meet the needs of your turf. This is
the same procedure that professionals use to determine operational efficiencies
of large-scale farm sprinkler systems.
You will need a few simple tools. Some you may have around the home. Some you may have to buy. However, you can do this evaluation for about $20.00 and in about an hour total time.
The first thing we will need is a timing device. You can use your microwave or oven timer, or get a simple wind-up timer like shown below. Or if you have a digital watch you can use it.
The next item you will need is a number of catch cans.
A straight-sided coffee can or a straight-sided coffee cup could be used.
The easiest tool to use is a simple rain gauge. Inexpensive gauges are
about $2.00 and can be found in many garden stores across the state. You
will need at least 10 gauges.
Now we need a sprinkler. Here is just one of many that
you may have.
The next thing we need to do is set up the yard for the evaluation. Turn the sprinkler on for one complete cycle (back and forth). Mark the very outside edge of the sprinkler pattern. Just use a can for this. Turn the sprinkler off. Now, measure five (5) feet out from the sprinkler. Place the first catch can (rain gauge) at that point. Then put another catch can (rain gauge) every five feet in a straight line out to the very edge of the sprinkler pattern. Your yard should look like the next photo. The more catch cans you use, the better the evaluation becomes.
Now comes the hard work. Let the sprinkler system run for between 15 and 30 minutes. Just pick one. If you are seeing a large volume of water appearing in the catch cans, go for 15 minutes. If the volume caught is not as great, use the 30-minute time.
At the end of the time, turn off your water. Then, using a sheet of paper and pencil (pen), measure and record the water depth in each container. If you used rain gauges, this is easy - just read off the depth directly. If using cans or cups, you will need a ruler of some type. Just make sure it reads in 1/16th of an inch.
I used a rain gauge to do my yard. And no, my water is
really not purple. I added food coloring to make it show up on film.
There are two ways to finish this project. Add up all the readings you have and divide by the total number of catch cans you used. This will give you an average "precipitation" rate for your sprinkler. By doing it this way, you can actually determine how "efficient" your sprinkler is. You can see dry or wet spots in the sprinkler pattern. Or, you can pour all the water into one container, record the total amount and then divide by the number of containers used. Either way, you get the precipitation rate for that sprinkler in either 15 or 30 minutes. The final number could look like (.15 inches in 15 minutes). This is the key number. You would use that number with the ET number presented in several newspapers, Channel 8, or the radio in the Toms River area. Or you would join the R.I.S.E. network of weather stations and obtain the ET number right from your nearest weather station.
It is best to water on a three or four day cycle. In New Jersey, most of the state is on an odd-even cycle. Therefore four days is probably best. Now this can actually be every other day if you have a large front yard and a large back yard. Just do the backyard every four days and the front yard every four days; you will just be watering every odd or even day.
If the ET for the last four days were 1.2 inches, and your sprinkler system applied .4 inches per hour, then it would have to run 3 hours in each location of your yard to refill the root zone with the water that your grass used. What you may want to consider is finding a sprinkler that would apply more water per hour to cut down the number of hours you actually run the sprinkler in each location.
In the home hose-end market, this can be a daunting task. You may have to buy and evaluate a few sprinklers before finding the best one for your yard. Permanent underground sprinklers are not as difficult to determine. The makers of your system and your installer can tell you your precipitation rate and help you make these calculations. But either way, you can do it.
A final word. When selecting a sprinkler, just try and
match its output to the intake rate of your soil. A sandy soil could handle
probably an inch an hour rate. A heavier silt or clay soil could probably
only handle about a quarter inch an hour. Any more than that and you will
see puddles forming or water running into the gutter.