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26 November, 2007

General Drip Irrigation Guidelines (AKA Starting Points)

Some Suggested Watering Times to Start With:
Type of Plant Time (in hours) Intervals (in days)
Low Shrubs (2-3’)...........2...............3
Shrubs and trees (3-5’).....3...............4
Shrubs and trees (5-10’)....4...............5
Trees (20’ and over)........5...............6
Flower beds.................1...............2
Ground covers...............1...............2
Vegetables – close spacing .5-1.............2
(That's point 5, or 1/2 to 1 hour.)
Vegetables – wide spacing 1.5..............2
Potted plants..............1-10 mins........1

Selection, Number and Spacing of Emitters
Flow Rate (GPH) Number of Emitters Placement of Emitters
Low shrubs (2-3’)-------1.0-----------------1-2----------------------At plant
Shrubs and trees (3-5’) 1.0------------------2-------------------1-12” either side
Shrubs and trees (5-10’)2.0------------------2-3-------------------2’ from trunk
Shrubs and trees (10-20’)2.0-----------------3-4-------------------3’ apart
Trees (over 20’)---------2.0-----------------6 or more-------------4’ apart
Flower beds -------------1.0-----------------1--------------------At plant
Groundcovers ------------1.0-----------------1--------------------At plant
Vegetables, closely spaced 0.5-1.0-----------1--------------------Every 12”
Vegetables, widely spaced 1.0-2.0-----------One per plant---------At plant

Remember, actual amounts of water will depend on soil type, composition, air and soil temperatures and presence or lack of humidity and wind. NOTHING takes the place of thoughtful, informed decisions made by you on the scene.


To plan your system correctly you will need to find out your available water supply (how many gallons per hour your system produces).
To do this, follow these steps.

1. Turn on the water supply all the way
2. Place a 5 gallon bucket in the water flow for set amount of time. Let’s use 30 seconds as an example.
3. At the end of 30 seconds take the bucket out of the water flow.
4. Turn off the water supply!
5. Check the bucket and estimate the amount of water in it.

Or, somewhat more precisely, measure it with a gallon milk jug. Let's say 1/2 of the 5 gallon bucket is full. Which means it’s half full and that would figure to be close to 2.5 gallons. Take the amount of water in the bucket (~2.5 gallons) and multiply it out for a full minute. In this example, there is 2.5 gallons of water in 30 seconds, or half a minute. Because we need the number of gallons per minute, use the calculation 2.5 x 2 = 5 gallons. (If 2.5 gallons of water in 15 seconds then we would have done 2.5 gallons x 4, because 15 seconds is ¼ of a minute.)

Take your answer and multiply it by 60. Our example would be 5 x 60 = 300. The 60 is for 60 minutes because we need the Gallons per Hour (GPH) of total water available. In our example we have 300 gallons per hour (GPH) available for our system. At no point, can you exceed that limit of 300 gallons per hour and still have an efficient system. That would be the equivalent of 300 one GPH emitters on one valve at one time.

It is impossible to state an approximate of GPH available at any given tap in LA – some areas have tremendous water pressure, but you can be in such an area with old pipes and a poorly designed system that reduces that wonderful water pressure down to a drizzle. The only way to know is turn the water on and see what you have there.

If water pressure is a problem, which would be rare in a city setting, simply use more valves with fewer drippers.

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