Friction Loss - Supply Section
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Discussion of Analysis
The purpose of the last two lines on the Friction Loss Analysis page is to summarize the design (or proposed design) as to whether a modification is appropriate. These comments are an overall rating of the two basic sections of the irrigation system: Supply & Feeder.

The percent of pressure loss across the Supply Sections is the factor that determines this rating. Maintaining as much of the inital water pressure after the flow has passed through the primary and secondary supply sections is vital in order to provide the maximum of stability and function in the terminating "feeder sections"

When the pressure loss for these sections is less than 10%, this allows sufficient pressure to provide flexibility for the feeder sections and future expansion.

Supply Design - "Good"
When the percent of pressure loss across
the Supply Sections is than 10%
this classifies for a rating of "Good"

Supply Design - "Fair"
When the percent of pressure loss across
the Supply Sections is greater than
10% but less than 18% then this classifies
for a rating of "Fair"

Supply Design - "Poor"
When the percent of pressure loss across
the Supply Sections is greater than
18% but less than 25% then this classifies
for a rating of "Poor"


Supply Design Analysis is "Bad"
When the percent of pressure loss across
the Supply Sections is greater than
25% then this classifies for a rating of "Bad"


In order to reduce the pressure loss from the supply lines in an irrigation system, the "Feeder" sections combined demand needs to be reduced. This can be done by using emitters with a slower flow rate. Usually shortening the Supply lines or reducing the number of emitters causes more problems than it solves.
In some situations, of course, it may be necessary to install additional Supply lines, or a supply line with larger diameter. Typical residential installations use 3/4 inch valves that are capable of delivering up to 20 to 28 gpm (or about 1500 gph).


Water Pressure & Water Flow
As is obvious from the image below, the same
pressure compensated emitter will flow at very
different flow rates when the pressure feeding
that emitter changes.



Simply because the soil is wet where the emitters are placed, does not assure that the correct amount of water is being applied.

Inconsistant water flow rates across an irrigation system basically assures that some plants will get too much water while others don't get enough.



Predictable Flow Rates
=
Healthier Landscapes

Irrigation Flow Rate Factor
 The speed at which the irrigation water applied
measured in Gallons per Hour
per Square Foot (gph/sqft)
has a major impact on the wetting
and moisturizing pattern within the soil.


The movement of moisture downward through
the soil is limited by that particular
soil's Hydraulic Condutivity [HCR] rating.
When water is applied in excess of that speed,
there is no place for it to go but sideways.
Water does move sideways to a degree anyway
from osmotic pressure, but this is smaller than
the force of gravity on the water.

When the HCR has been exceeded
and sideways movement is excellerated
The resulting moisture pattern will look similar
to those shown in the graphic above.
This results in wasted water, and encouraging
the growth of weeds.

Therefore Matching Irrigation Application flow
to the HCR of the soil is essential.
This is the primary benefit to utilizing
the Irrigation Matching Calcultaors found in the
Irrigation & Soil Matching Calculators
"I&S-M Pro-I."

How many Minutes to get
How many Gallons?
Remember "how many minutes" will need to vary with the number and flow rate of the emitters you use. Most emitters are rated in gallons or fractions of a gallon per hour.

When the water pressure to an emitter changes (or is unknown) then the emitter's rating doesn't mean much. WE need to design with stable and reliable water pressure. The Six Point Friction Loss Calculator provides the information needed to design irrigation system flow properly, so as to know the output of the various emitters.

We program the controller in run-time minutes, yet what we are concerned with is gallons of water applied. To effectively get the water to penetrate deeply, we need to allow enough time to avoid water spreading to areas not in need of water.

The complexity of setting run time is easily delt with through the use of the "I&S-M Pro-I" calculators. Relying on guess work for scheduling irrigation controllers and clocks is an expensive idea. Both in the health of the plants involved, and the amount of water effectively used or wasted.