Useful Irrigation Formulas & Charts - The Urban Farmer Store

Useful Irrigation Formulas & Charts

Application Rates of Emitter-Line Grids ? This simple formula allows the precise calculation of application rates in inches per hour. Just enter the emitter rate (GPH), the spacing of the emitter-line that you are using in inches, and the spacing of the laterals in inches into the formula.

Application Rates of Point source Drip Systems ? This formula is for systems using individual emitters. You add up the total GPH of all the emitters on the valve and enter that total along with the area watered in square feet to get your application rate in inches per hour.

= Application Rate (inches/hour)

GPH X 1.604 Area

(square feet)

Common Emitter-Line Spacing Chart ? This chart shows the application rate and run times to apply a quarter inch of water. The emitter lines chosen are the most commonly sold and used.

COMMON EMITTER-LINE SPACING CHART

Emitter spacing

Header

Lateral Spacing

Maximum Length of a Single Lateral (feet) ? This chart is for knowing the longest a lateral for 17mm emitter line that is pressure compensating and has check valves. We know it most commonly as Netifim's Techline CV, but the chart works with new 17mm products by Hunter, NDS (Agrifim) and RainBird.

MAXIMUM LENGTH OF A SINGLE LATERAL (FEET)

Useful Irrigation Formulas & Charts

Proper Size of Headers and Lateral Lines ? Headers and laterals need to be sized for the volume of water going through them. If sized too small there will be excessive pressure loss and increased velocity that can produce water hammer. Remember to divide GPH in your drip systems by 60 to get gallon per minute.

PROPER SIZING OF HEADERS AND LATERAL LINES

GPM* Pipe Size Sch.40 0-5 GPM ?" PVC or Poly 5.1-8 GPM ?" PVC or Poly 8.1-13 GPM 1" PVC 13.1-22 GPM 1 ?" PVC 22.1-31 GPM 1 ?" PVC

* for gph, multiply gpm by 60

Total feet of emitterline needed for a given area (square feet)

12 inch lateral spacing ? 1 X square feet 18 inch lateral spacing ? .66 X square feet 24 inch lateral spacing ? .5 X square feet

Run Times for both Sprinkler and Drip Systems ? If you know the precipitation rate in inches per hour of your system and how much water you wish to apply in inches this formula will give you the run time in minutes.

= RunTime

Water Requirement X 60 Precipitation Rate

(Inches Per Hour)

Precipitation Rates of Sprinkler Systems ? Most of us rely on the precipitation rates from manufactures' catalogs. But with single stream rotors we often can use this formula to be more precise. We add up the total gpm's of the sprinklers used and calculate the square feet of the area watered. We enter those in the formula to get inches per hour.

= Precipitation Rate (inches/hour)

GPM X 96.3 Area

(square feet)

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