Watering needs vary according to soil conditions, exposure to sun, wind and shade, and plant material.
(1) The first step to operating your sprinkler system is to identify the sections of sprinklers and their characteristics, and identify the basic characteristics of the heads in each section.
| No | Location | Heads | Type of Area |
| 1 | Front Lawn South | Spray | sunny |
| 2 | Front Lawn North | Spray | sunny |
| 3 | Shrubs next to front of house | Spray | shade |
| 4 | Back Lawn | Rotors | sunny |
| 5 | Back Slope | Rotors | ivy |
| 6 | Hanging Pots | Micro spray | shade |
(2) Next make an estimate of the time it takes to apply one inch of water with the heads on each section.
As a rough rule of thumb about 1 inch of water per week is required over all planting areas in the spring and fall, going up to 2 inches in the warmer part of the summer. The following chart gives very rough estimates of the number of minutes it takes to apply one inch of water according to the spacing of heads, assuming the heads are properly spaced for head-to-head coverage. Older system typically require reducing the number of minutes for one inch, especially for heads spaced close together – 3 to 8 feet. Some older systems take only 2 minutes to apply one inch for heads spaced at three feet in a narrow bed.
| Type of Head | Spacing | Minutes for 1 inch |
| Typical lawn spray head | 8 to 15 feet | 40 |
| Typical shrub spray head | 8 to 15 feet | 40 |
| Rotor head for lawn or shrub | 20 to 40 feet | 120 |
(3)
Divide the watering time for the number of applications per week. Most soils can absorb only about ½ inch of water per hour. Spray heads put out water at a rate of 1-1/2 to 3 inches per hour. Effective watering requires applications two or three times per week. Shallow rooted annuals and dichondra lawns may do better with daily watering. Shrub areas can often be watered less frequently than lawns. The most common frequency is 3 times per week. Steep slopes with run-of or erosion problems are sometimes set to water 2 or more times on whatever days they water to reduce the rate of application.
The final chart might look something like this:
| No. | Location | Heads | Type of Area | Time for 1 inch | Frequency | Time |
| 1 | Front lawn south | Spray | sunny | 40 | MWF | 13 |
| 2 | Front lawn north | Spray | sunny | 40 | MWF | 13 |
| 3 | Shrubs next to front of house | Spray | shade | 40 | MWF | 8 |
| 4 | Back lawn | Rotors | sunny | 120 | MWF | 40 |
| 5 | Back slope | Rotors | ivy | 120 | F | 40 |
| 6 | Hanging pots | Micro sprays | shade | n/a | Daily | 5 |
(4) Vary the time according to the season of the year or current weather patterns. Typically people double the time for the hot part of the summer, and cut it back to minimum time for the winter. (When possible it is best to keep the system running regularly all year around for at least a minimum amount of time to keep the solenoids on the automatic valves from corroding, which sometimes causes valves to stick when activated).
(5) Adjust settings for individual section differences.
After the initial settings, check the sections to see if they appear to be getting too much or too little water and adjust the timing for each section accordingly.
(6) Select the time of day to start watering. There is wide agreement that early morning is the preferred time to water. Evening watering is thought to promote night-time bug activity. Mid-day watering promotes burning of plant material as the hot sun is magnified through the droplets, and evaporation and wind conditions are usually more favorable in the early morning. Most people want to finish watering by 8:00 a.m., and some by sunrise. Some communities require watering to be over by a certain time, usually 8:00 a.m. or 10:00 a.m.. Add up all the times for all the stations that will water on a given day. Subtract the number of minutes of total watering time from the time you want to be finished by, and set the start time accordingly. Most people seem to prefer to start around 5:00 a.m., while some large properties start at midnight. Remember to coordinate your watering schedule with the delivery of your morning paper if it is likely to get wet.
(7) Seasonal changes can take a lot of time to make if each section is adjusted individually. Some of the newer controllers have a feature called "water budgeting." The purpose of this feature is to allow increasing or decreasing the run times of all sections by a percentage with a single setting. If you set your controller for spring and fall watering based on the one inch of precipitation per week, and let that be the 100% setting, then increasing the budgeting setting to 200% in summer will double the watering times for all stations. In the rainy season you can set the budget setting to 10%, or set the controller to the "rain" or "rain-off" setting to shut down completely.
If your controller does not have the water budgeting feature, a similar effect can be achieved by adding a second start time in the summer, which effectively doubles the watering for all the stations. I f you are using more than one program (schedule) on the controller, you need to set a second start time for each program. Another way to change watering time without changing all stations individually is to add or deduct watering days from the schedule. Thus going from 3 days a week to 6 days will double the watering time.
Hammer Company, Inc.
1645 Euclid St., Santa Monica, CA 90404
(800) 660-1452 (310) 450-1122
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