Figuring out when and how much water to put down on your lawn is one of the trickier parts, and potentially expensive parts, of home ownership. Whether or not you have a sprinkler system or are planning to do it with good ole fashioned hand watering, knowing the key principles behind ideal watering can save yourself time and money. Even if you have installed the most state of the art sprinkler system, it will only be as good as the schedule it has programmed in.
• How Much to Water
It is better to water longer with less frequency than to water often for short amounts of time. This is because short watering’s will lose a significant portion to evaporation whereas a longer watering gives the soil time to soak it in. It takes approximately one inch of water to soak 6 inches down into the soil.
Most lawns and plant material should be deeply watered 2-3 times a week while allowing time in between watering’s for the soil to dry out. All roots need water but just as critical is oxygen. If the soil never has a chance to dry out it will start to decline because the plant cannot get all the oxygen it needs from its leafs.
• Time of Day
It is best to irrigate between 10pm and 7am. This is considered the sweet spot of watering because it is when temperatures are normally lowest and winds have calmed down. Another benefit of this is that it coincides with the plants natural dew periods. Watering outside of this time will extend the dew period, which can encourage disease as well as increase water lose due to evaporation.
• Always Check Water Penetration.
You cannot assume that just because it looks wet it has gone deep enough. This is especially true when we get a rain squall. People will assume that because it has rained they don’t have to worry about watering. What they don’t realize is that this rain has most likely just hit the top of the soil and has not gone any deeper. We highly recommend using a long flat bladed screwdriver as a probing tool to determine watering depth. If you push the screwdriver down into your soil before and after watering you will be able to tell how far down the water has soaked. 6 inches is the ideal depth.
• Not All Sites Are the Same
This sounds obvious but it is important. Many things will affect absorption rate: soil type, slope, mowing height, microclimates (aka, full sun vs. little sun, under a tree, near sidewalks etc.…)
The way your neighbor needs to water his yard may be completely different than the way you will need to water yours.
• You Might Not be Able to Water All at Once
In areas that cannot soak in that much water in one time it is better to water in two cycles for half the time than to water it all at once. This simply means having 2 start times (cycles of your zones) but splitting the time in half for each run. The total time obviously comes out the same which is intended to produce the full 1 inch of irrigation in each zone. The example for rotor heads would be to have 2 cycles of 40 minutes totaling 80 minutes. Both of these cycles run back to back, meaning your system may start up at approximately 10:00 PM for the first cycle and the second cycle begins just as the first one ends. Ideally these two cycles occur from about 10 PM to about 7 AM.
How to Measure Water Output
The best thing to do is to set out a can or straight-sided tupperware in reach of each sprinkler head for automated systems or in the reach of whatever sprinkler you plan to use for hand watering. Let them run for a half an hour and then measure in inches how much water you have collected. Multiply that number by 2 and then divide by 60 and you will have how many inches of water that sprinkler is putting out per minute. Divide the number one by the number you calculated and you will then have the number of minutes you need to run your sprinkler in order to get 1 inch of water down.
Your measure that your sprinkler put out 0.4 inches of water down in 30 minutes.
Multiply 0.4 X 2 = 0 .8 inches in one hour
Divide 0.8 / 60 = 0 .01333 inches of water put down in 1 minute
Then Divide 1 / 0 .01333 = 75 minutes to get 1 inch of water down
The next thing is to apply these principles to your watering schedule. First measure and calculate how long each of your sprinklers or heads take to put out an inch of water. Now you know how long it will take to water each area. Accomplishing this can be much trickier/ time consuming at first when having to set up zones on a sprinkler clock than when doing it by hand but once you have it set you get to just sit back and enjoy.
For those who want to tackle setting their sprinkler clock themselves I have outlined how to approach most controller programming for 1-8 zone systems and a separate one for those with 9 or more zones.
1-8 Zones Controller Programming
1. Set each station run time to half of the required total minutes needed to achieve 1 inch of water
2. Set days to water on three days out of the week. (odd or even days if city ordinance requires). Be sure to leave one dry day when you are not doing any watering.
3. Set start time #1 at 10:00 PM and start time #2 later than 12:00 AM by the number of total minutes all zones. This will usually be three or four hours later.
4. If you have drip irrigation, these zones should be the last zones to water since they may run much longer during morning hours. If desired, the zones can be programmed to be on Program B separately from your lawn zones.
Your system should now be set up to water three days out of the week. It should come on at 12 o’clock midnight and water one full cycle, then as it completes run another full cycle and finish approximately between 6:00 AM and 8:00 AM. These two cycles combined should provide the total minutes indicated earlier for each type of head. Again, as you watch your system wet areas can be reduced in minutes and drier areas can be increased as needed.
9+ Sprinkler Zone Controller Programming
For larger sprinkler systems of nine zones or more, it will be impossible to water the recommended times within the “sweet spot” entirely in one night. By dividing the total number of zones into groups (programs), you can still accomplish most of your watering during the sweet spot. Only two programs (A and B) would be required for up to 12 zone systems. For systems with more than 12 zones, better results can be achieved by dividing into three programs (A, B, and C). This of course assumes that you have this capability on your controller (most modern controllers have this capability). Zones are equally divided into groups by the total time required. Each program, however, must run on different days of the week from the other programs. Otherwise each program will be set up as explained in the Double Split Start Time Concept.
2 program systems: (three days per week on each program and one dry day)
3 program systems: (two days per week on three programs and one dry day)
1. Set each station’s run time to half of the required total minutes needed to achieve 1 inch of water
2 Programs: Set days to water on each program to 3 days out of the week. (odd or even days if city ordinance requires). Be sure to leave one dry day for your mowing.
3 Programs: Set days to water on each program to 2 days out of the week (this setting may prevent you from meeting city restrictions that limit the days of week). Be sure to leave one dry day for your mowing.
Set start time #1 at 10:00 PM and start time #2 later than 12:00 AM by the number of total minutes all zones. This will usually be three or four hours later.
2. If you have drip irrigation, these zones should be the last zones to water in any of the programs since they may run much longer during morning hours.
Your system should now be set up to water two or three days out of the week depending on how many programs. It should come on at 12 o’clock midnight and water one full cycle, then as it completes run another full cycle and finish approximately between 6:00 AM and 8:00 AM. These two cycles combined should provide the total minutes indicated earlier for each type of head. Again, as you watch your system wet areas can be reduced in minutes and drier areas can be increased as needed.
Wrap up thoughts:
Some conditions such as poor water pressure, poor head spacing, etc. require ingenious ways to circumvent those situations. Sometimes sprinkler system design is inadequate, or trees, shrubs or other plant material may block head coverage or roots can pinch underground sprinkler pipes and adversely affect the performance of your system. Modifications are required in these cases. You may want to consult further with sprinkler specialists if you have experienced unusual difficulties.
LawnTech can provide free price quotes for any adjustments or modification needed. Please feel free to give us a call! Happy Watering!