Page 40 - Grapevine May-June 2020

Around The Vineyard

system and even a small failure leads to plugging
downstream. If filters plug rapidly one solution is
to install greater surface area of filtration to spread
the load. Increasing the frequency of cleaning the
filters is also important. When troubleshooting irri-
gation system performance problems, considering
the adequacy of the filter station is important. It
is common to install a filter that is too small for
the particulate load to reduce cost of the system
install, but this increases costs in the long run due
to down time and emitter plugging downstream.

The higher the frequency of cleaning filters, the
higher the DU score. Filters need to be cleaned reg-
ularly during the irrigation season. It is not enough
to simply back flush filters regularly. Back flushing
should be viewed as a secondary form of clean-
ing, not the primary type of filter maintenance.
Screen filters must be physically cleaned and the
sand in sand media filters must be monitored and
replaced. Any pressure drop greater than five psi
across the filter is a sign that there is material plug-
ging the filter and it could be cleaner. One vineyard
with a high scoring system removes the screens
from their screen filters and pressure washes them
several times during the irrigation season.

Although almost all drip emitters on the market
today are pressure compensating emitters, pres-
sure variability still effects system performance.
In this study, many systems were found to have
pressures in the field that varied from below the
minimum to above the maximum specifications
for the emitters installed. This leads to flows lower
or higher than expected. In the case of low pres-
sure, it can also be associated with inadequate
flow rates. In the case of high pressures, it can be
associated with blowouts. Installing or replacing
pressure regulators can even out the pressures in
the field and improve system performance. Consult
the system design for reasonable target pressures
in the drip line. Generally speaking, the pressure
at the farthest point from the pump or the highest
point in the system should be above 8 psi to ensure
emitters are functioning properly.

The Benefits

The benefits of properly equipping and main-

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