Friction Loss - Feeder 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 at the Feeder Section is the factor that determines this rating. The input pressure to the Feeder section is provided by the Supply Section. Maintaining enough pressure that the terminating emitters can effectively provide 80% of their rated flow is very important.
Below this level attempting to achieve a predictable volume of water to the plant area becomes difficult. Additionally this lower pressure creates the opportunity for larger discrepancies between emitters of equal ratings.

When the pressure loss for these sections is less than 15%, this allows sufficient pressure to provide flexibility for future emitter increases.

Supply Design - "Good"
When the percent of pressure loss across
the Feeder Section is than 15%
this classifies for a rating of "Good"

Supply Design - "Fair"
When the percent of pressure loss across
the Feeder Section is greater than
15% but less than 22% then this classifies
for a rating of "Fair"

Supply Design - "Poor"
When the percent of pressure loss across
the Feeder Section is greater than
22% but less than 33% 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
33% then this classifies for a rating of "Bad"


In order to reduce the pressure loss from the Feeder Section lines and emitters in an irrigation system, There are several changes that will help.

One is to utilize emitters with a slower flow rate (if possible). Another option is to reduce the length of the "feeder" line(s), or run two feeders; one to each end of the dripperline (if used).

Usually reducing the number of emitters causes more problems than it solves, but as long as the distribution of moisture is not adversely affected and a longer run time can be used - this will help.
In some situations, it may be necessary to install two feeder sections for the same planting area.


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.