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How Landscape Irrigation Works


Landscape Irrigation Design

A Most Capable Man and Building a Better Pop-up

During the eighteenth century in Britain, the man you might have wanted to hire to plan your garden was Lancelot Brown, also known as “Capability Brown.” Brown made sure that the landscapes appeared to be natural and unplanned, even studying architecture to be sure his designs conveyed the classical idea of unity. One of his greatest works was Blenheim Palace, where British Prime Minister Sir Winston Churchill was born. Not bad for a man who began his career as a gardener's boy [source: Encyclopedia Britannica].

Once upon a time, spray heads didn't effectively water the area closest to the sprinkler, leaving brown circles on green lawns. Newer pop-up spray heads come with nozzles that have undercut sprays, a second opening beneath the main nozzle. This feature mitigates the problem of those unattractive brown patches [source: Tucker].

You're going to want to use graph paper to plan out your space. Figure out a system that will work for you, such as one square equals one foot. Draw your landscape on the graph paper. It's usually a good idea to use a pencil for your drawing, in case you change your mind.

You have two major choices when designing a landscape irrigation plan. If you have clearly defined geometric spaces (most lawns are squares or rectangles), you'll likely choose rectangular spacing. For purposes of irrigation design, sidewalks or driveways are irrelevant. The sprinklers will sit along the perimeters and in the corners, as well as any place where the imaginary grid lines intersect [source: Roberts].

Let's say, however, that you're dealing with an irregular-shaped lawn. A plan that uses triangular spacing will work best. Rather than marking off square grids, your design should be based on equilateral -- all sides are the same length -- triangles. This method generally offers better coverage than rectangular spacing does, even though there's likely to be at least one sprinkler that sends water farther out than you need. Figure the distance between the rows of sprinklers by multiplying the distance between sprinklers by .866 [source: Roberts].

How far apart the rows are is determined by the rating of the sprinkler head. You're aiming for coverage that goes from sprinkler head to sprinkler head. Don't worry, some overlap isn't bad. If the system you're looking at says it will throw water at a radius of 30 feet, take that with a grain of salt. These sprinkler heads are tested in prime conditions. If you live in a windy area, for example, that wind is going to blow the water and affect coverage.

Congratulations! Now you finally understand how your high school geometry class fits into the real world. Now it's time to check out pumps and sprinkler heads.