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Drip irrigation or sprinklers...
which is better
?
Of course there is no panacea, no one
"right answer". It all depends on your situation.
"Drip irrigation" is a term that's often
used to mean much more. It can describe a few different ways of
applying water at lower flow and pressure than
conventional sprinklers. Other terms sometimes used include
"low volume" and "micro" irrigation.
Drip irrigation is water applied to the root
zone using a variety of devices first pioneered in agriculture and
later adapted for landscape use. These included emitters,
soaker lines, and even micro-spray heads.
Drip irrigation tends to apply water more efficiently,
but is often more subject to damage from shovels, rakes, and
occasional squirrels and other rodents because it is installed
at or just below the surface of the ground.
Drip also requires a maintenance commitment. Filters
need to be cleaned regularly and emitters need to be checked and
occasionally replaced.
True drip irrigation
is most useful for shrubs, trees and container plants.
"Micro-sprays" are a hybrid between drip and spray heads, and
an option for dense groundcover and shallow rooted annuals and
perennials.
The keys to effective drip irrigation are
good filtration and pressure regulation.
Let's take a look at how drip and conventional
sprinklers compare.
Drip
Irrigation |
Sprinklers |
Lower materials
costs. |
Higher initial materials costs. |
Easier to install, modify and repair. |
More work, and disruptive to the landscape to
modify. |
Frequent monitoring and maintenance. "Hard
water" mineral content can be problematic. |
More durable components. Infrequent maintenance and
repairs. |
Less run-off, water applied slowly at root
zone. |
Quicker run-off, more potential for water
wasted. |
| Longer run times usually necessary
for thorough watering. |
Shorter run times per station, more
stations watered in a limited time
period. |
Better for deeper rooted trees and shrubs. Good
for container plants. |
Better for shallow, spreading
roots: annuals, many groundcovers and
perennials |
Filters...
Because water is applied via small holes, good
drip filtration is an absolute must!
Sand, grit, rust from old galvanized pipes and
mineral deposits from hard water can all contribute to clogging.
We prefer 150 mesh stainless steel or nylon
in-line filters. Filters should be checked and cleaned at the
beginning of the watering season, and again during the warmer months
when watering is more frequent.
Pressure
regulators...
There are two kinds of pressure regulators,
fixed (or pre-set) and adjustable.
Fixed regulators are installed after individual
valves and are more economical where one drip valve is isolated, or
in a group with other sprinkler valves. Generally they only reduce pressure by a factor of three,
i.e., 90 PSI > 30 PSI.
Adjustable regulators
are useful for mainlines under constant pressure. They are
more economical in situations where several drip irrigation
valves are grouped together.
Drip irrigation works best at or below 30 PSI,
therefore if your unregulated water pressure exceeds 90 PSI, an
adjustable filter with a range of 25 PSI to 125 PSI and an incoming
pressure capacity of at least 150 PSI is recommended.
Tubing...
Drip irrigation most often uses flexible black
polyethylene and vinyl tubing and compression fittings, which
require no glues or solvents. Emitters and other watering devices
have barbed ends which insert into small holes pierced in the
tubing. 
In most instances, tubing is installed at
ground level and covered with mulch.
Emitters...
A wide assortment is available, some
self-flushing, some pressure-compensating (best for slopes), some
using diaphragms, some using 'turbulent flow', all attempting to
achieve even water distribution. Emitters come as either
single or multiple-outlet styles.
Some systems actually incorporate emitters
within the tubing, spaced at 12, 24 or 36 inches. These are
especially useful for long hedges, shrubs on a slope, stands of
trees, or outlying areas.
© Copyright 2003, 2004, G. Catanese Landscape
Services
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