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Draw In Sprinklers
09/10/10
You're now ready to pencil in the sprinkler head locations on your drawing.
Hallelujah! I know it seems like it took a long time to get here, but to do
a good job we needed to cover a lot of background information! Use a pencil
to draw in the sprinkler heads so you can easily make adjustments to the locations
later. Many people find it helpful to use a compass to draw a light pencil line
showing the radius of water throw for each head.
Remember these tips:
* Keep the distance as uniform as possible between heads. To the extent possible
a sprinkler should be equal distance from the adjacent sprinkler in each direction
(forming a triangle if possible). Changes in spacing between adjacent sprinklers
should be made as a gradual transition when possible.
* Try to position heads so that if you were to draw a straight line between
adjacent heads they would form an equilateral triangle (each side of triangle
is same length). This is called "triangular spacing" and creates more
even water coverage than "square spacing" (ie; lines between 4 heads
form a square). That said, you will often be unable to form a triangle so don't
panic if you can't.
* Don't stretch the spacings, use "head to head" spacing. Using
too many sprinkler heads is seldom a problem, using too few sprinklers heads
is ALWAYS a disaster!
* Start by drawing a sprinkler in each corner. Next, draw sprinklers around
the perimeter of the irrigated area, watching that they are not too far apart
(one more time, better too many than too few!). Adjust the locations to make
the spacing between sprinklers as even as possible. After the perimeters are
done, then draw the sprinklers in the interior area.
* If the sprinklers need to overlap so that the spray from one head goes over
and beyond the next that's OK. While you don't want to over-water, it is always
easier to correct an over watered area than a under watered one. For example,
you can use the radius adjustments on the sprinklers to cut down the water in
the over-irrigated areas. If need be you can even remove or relocate a sprinkler
later. It's much easier to remove one than to add one!
* Sprinklers that are placed closer than 6 feet apart need some special consideration.
Standard spray-type sprinklers don't work well if the radius is adjusted below
6 feet. (The opening the water goes through is so tiny that the normal expansion
of the plastic or metal on a warm evening can close off the water flow!) If
the area is long and narrow (4' wide or less), use the strip pattern nozzles.
I prefer the so called "side-strip" type that you place along the
edge of the area, they have better patterns than the center strip nozzles. End-strip
nozzles have notoriously bad patterns, they shouldn't be more than 10' from
the next head! When using standard spray sprinklers (like quarter, half, and
full circles) in areas where the radius must be adjusted to less than 6 feet
use a "pressure compensating device" to reduce the radius. The pressure
compensating device is normally installed under the nozzle where it reduces
the flow and pressure through the nozzle. The good news is that by using a under
sized pressure compensating device you can also reduce the nozzle radius! Unlike
the adjustment screw on the nozzle these devices work well regardless of the
temperature. However, you will need to select the proper size pressure compensating
device for each nozzle. It is possible that every nozzle will need a different
size! To select the right device you use a special chart provided by the pressure
compensating device's manufacturer. The chart will tell you exactly which device
you must use with each different nozzle in order to get the radius you want.
Most major sprinkler manufacturer's make pressure compensating devices for their
spray sprinklers, and the charts you need can be found in their catalogs. You
may need to go to a commercial sprinkler supplier to find them.
Study the example drawing below.
Uniformity is good!
Again, notice that the radius of each sprinkler's spray goes all the way to
the next sprinkler! This is critical.
Note that in the example above only the lawn area outlined with a green curving
edge is being watered. The area between the lawn (green line) and the edge of
the property (brown line) would most likely be planted with shrubs and irrigated
separately from the lawn. In most cases a drip system would be considered for
watering the shrubs as it is less expensive and more efficient. See the separate
guidelines for designing drip irrigation systems.
Bonus landscape design tip: Creating a border of shrubs around the perimeter
of your yard is, in most cases, a good landscape design practice. A shrub border
helps to reduce the visual impact of the fence (assuming that like most residential
properties you have a fence.) Shrubs also typically use less than half the water
of lawn areas of the same size, saving money spent for water. Once a month you
need to weed and trim shrub areas, as opposed to the lawn that needs to be mowed
every other week at the least in summer. A border using shrubs of various sizes,
textures and colors can add greatly to the attractiveness of your yard. Place
smaller shrubs near the lawn, with larger growing varieties behind them next
to the fence.
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