Designing a Sprinkler System
A smartly designed sprinkler system can keep your lush summer lawn strong, green and healthy.
The first and one of the most important steps in designing a sprinkler system is to gather information. A mistake at this point in the process will affect everything else, so accuracy and care are important.
Many irrigation system problems are traced back to inaccurate measurement of the area to be irrigated, so use a measuring tape or other reliable measuring device to get started. Go ahead and round off numbers to the nearest foot, but keep in mind that a minor deviation of a couple of feet can result in dry spots. Draw the area to be irrigated to scale on a piece of graph paper as you measure it. Use a scale of 1 square = 1 foot, or 1 square = 5 feet, if needed. Drawing as you go allows you to quickly catch errors.
If there is a building adjoining the irrigated area, start by measuring the building’s perimeter. Most buildings are built with square corners and straight sides, which gives you a good, accurate base for the rest of your measurements.
Measure the distance in a straight line from each corner of the building to the edge of the area to be irrigated. Draw in property lines and double-check everything by measuring the length of each actual property line.
Next, draw in the other items that are present in the area. For example, you would need to show the edges of lawns, tree locations, the location of your pool house, etc. With these items on the graph, you have a map of where you can and cannot plan the irrigation lines.
Measure the Water Supply
The next step is to measure the water supply. In the United States, water pressure is measured in pounds per square inch (PSI), and water flow is measured in gallons per minute (GPM).
Water pressure is the energy that powers your sprinkler system, so it is very important. If you work with it, it will make your sprinklers do the “rain dance.” If you ignore it, it can bite you hard in the wallet.
Water flow is the traveling companion of water pressure. Pressure is the “energy” that moves water through the pipes. Flow is the measurement of how much water is moved in a given amount of time.
You want to start by figuring out what the maximum water supply would be if you had perfect conditions, such as a very short pipe from the water meter to your house, lots of water pressure, a small yard, etc. Then you’re going to modify that number to reflect your actual conditions (long pipe, lousy water pressure, etc… More on this later …). The end result will determine what the exact, optimum water supply is for designing your sprinkler system. This means the sprinkler system will use less water, last longer, and there won’t be dry spots. This will take a bit more work than “guesstimating,” but it will be worth it.
The method used to measure the water supply depends on the source of the water. The measuring process differs between (a) city water systems, (b) water pumped from a well, pond or creek, or (c) water from a tank or pond located up a hill. The specifics of measuring these different water sources are rather complicated and could easily occupy all the space for this magazine article. For a helpful, highly detailed (and free!) tutorial on measuring your water supply, complete with an easy-to-use Design Data Form, check out the web page www.irrigationtutorials.com, which is the source of information for this article. Once you have measured your water you will have determined a Maximum Available Flow (GPM) and what is called “Static Pressure” (PSI). You need to write these values down, you will need them later.
The next step is to select the irrigation equipment. There are multiple components of a sprinkler system and multiple options for each component. Here’s a look at the basics.