THE HANDYMAN : Tired of Hauling Hose? Maybe It’s Time for a Sprinkler System
Spring in Southern California, while a season of overcast mornings, is the time to start aggressively watering and feeding lawns and shrubbery to get them ready for the heat of summer.
It’s also a good time to consider a permanent sprinkler system.
While installing an in-ground system can seem daunting, there really is nothing to it.
Dale Rahn knows--he’s in the midst of putting in the third in-ground sprinkler system since he and his wife, Suzanne, moved into their 1930 Spanish revival home in Orange’s Old Towne 9 years ago.
Dale--the vice president of a wholesale nursery company and the holder of a degree in ornamental horticulture and a certificate in landscape architecture--was undaunted by the ill-kempt back yard.
“It was wall-to-wall weeds, 3 feet tall,” he recalls. But Dale put his training to work and put in a small lawn, a large garden and a tiny orchard, all serviced by an in-ground sprinkler system.
A year later, the Rahns’ first child, Lauren, now 7, was born. Emily followed 2 1/2 years later and the layout of that pre-child yard soon stopped working.
It took a while to get started, but earlier this month, Dale finally began work on a redesigned yard that incorporates a more sophisticated landscape design.
One of his first chores, after ripping out the old landscaping, was to install a new sprinkler system. For ease of installation, and to keep costs down, Dale used PVC plastic pipe and fittings.
But he chose brass for the sprinkler heads and the all-important anti-siphon valves--a special shut-off valve required by building codes to keep water from the irrigation system from backing up into the household water lines.
Brass is tougher than plastic, so the exposed valves--which also turn the system on and off--won’t become brittle in the sunlight, as plastic valves can, and the sprinkler heads will hold up better than plastic.
Rahn’s system is more complex than many because of the curvature of the shrub beds that border the lawn. But for a relatively simple rectangular lawn area (you can modify the instructions for your own layout), here’s how to do it:
PLANNING Draw a plan of the yard layout, making sure to include the existing water supply into which you will hook your system (usually a hose bib).
Next, plot the location of your pipe lines and sprinkler heads. Remember, the more independent lines (a separate anti-siphon valve for each) you use, and the fewer sprinklers on each line, the better your water pressure will be.
There is a wide variety of sprinkler heads on the market, and each has different characteristics, so before you decide where to put them, choose a type and follow the manufacturer’s recommendations for spacing. Always space your sprinklers so there is plenty of overlap in the watering pattern. (See illustration.)
For lawns, use pop-up sprinklers--the nozzle that delivers the water pops up under pressure to clear the height of the surrounding lawn or ground cover. For shrubs, use standard fixed (non pop-up) shrub heads.
What usually works best are quarter circles in the corners and half-circles along the edges, spaced so the water patterns overlap by several feet. Fill in the center with rows of full circles.
PVC pipe comes in several different thicknesses and diameters. Most systems work best with 3/4-inch diameter pipe. Use “schedule 40” pipe for lines that will be constantly under pressure and the less expensive thin-walled “class 125” pipe for the rest of the system.
For a simple rectangular lawn 40 feet wide and 20 feet deep, using sprinkler heads with a maximum of 20 feet of coverage, you would need to install three rows of sprinklers along the 40-foot width, as illustrated. The watering patterns overlap, ensuring plenty of coverage and no dry spots.
TRENCHING After you’ve plotted the system and purchased the requisite pipe, fittings, valves, sprinkler heads and PVC primer and glue, it’s time to dig the trenches. They should be 6 to 8 inches deep, so you won’t risk cutting pipes if you later run a roto-tiller or cultivator over them. If you are using an extra-large sprinkler head, you may have to dig deeper. Check the measurement.
You can rent a trenching machine at most equipment rental yards, but a shovel works just as well. Dig your trenches as close to the edge of the lawn as possible and make sure to trench all the way up to your water connection. If you have to tunnel under a sidewalk, use a high-pressure nozzle on a hose to blast some dirt loose, then bore it out with a piece of steel pipe, blast again with water, bore with the pipe and keep repeating the process until you’ve drilled a hole right under the concrete.
VALVES Anti-siphon valves generally come with manufacturer’s instructions for installation. Remember to turn off the water to the house before you start making your connections to the water supply. For longevity, use galvanized pipe and fittings rather than plastic here. Valves should be installed 6 inches or more above the highest sprinkler head in the yard to keep water from flowing backward into the drinking supply (see illustration A).
SPRINKLERS To put your system together, first set the PVC pipe sections in the trenches, measure and mark on the pipes the location of each sprinkler and cut the pipe with a hacksaw or special PVC pipe cutter where the sprinkler heads are to go. Then assemble, using the proper fittings and special PVC primer and glue.
Use a threaded elbow for sprinkler heads at the end of a length of pipe and threaded “T” fitting for other sprinkler heads. On each type of fitting, the threaded arm, which takes a 1/2-inch diameter riser, points up--you later will screw the riser pipe into it (see illustrations B and C). Clean the cut ends of the pipe (use sandpaper to clean off burrs left by the hack saw) and liberally coat them with PVC primer. To glue PVC pipe properly, coat each piece to be glued with primer, then apply glue to both pieces (the outside of the pipe and the inside of the fitting) and slide pipe ends into the fittings as far as they will go. The glue melts the plastic and fuses the pieces together for a water-tight fit.
When you’ve got all the pipe sections joined and all the fittings for the sprinkler heads installed, screw one end of a short piece of threaded PVC or galvanized metal pipe--the riser--into the threaded opening in each “T” and screw your sprinkler head to the other end. The short riser should be long enough so that the top of the sprinkler head is at ground level when attached.
FINISHING When you have completed gluing the pipes and installing the sprinkler heads, join each line to its anti-siphon valve and then, before you fill in the trenches, turn on the water. Check your fittings for leaks (you will have to cut out and replace any that do) and make sure the sprinklers cover the lawn area thoroughly and evenly, with no dry spots. If the overlap is too great, use a small screwdriver on the slotted fitting in the center of each head to turn down the pressure.
To fill the trenches so they don’t leave a gully in your lawn, pack the dirt as firmly as possible, then water it and let it settle for several days. Pack it again, fill in any depressions, pack all that down and you are ready to plant your new lawn or replace the sod you removed if you installed the system in an existing lawn.
WHAT YOU NEED These are the supplies you will need to install a simple sprinkler system:
TOOLS
Shovel or trenching spade.
Sandpaper.
Adjustable pipe wrench.
Tape measure.
Hacksaw or special PVC pipe cutter, available at most home improvement or irrigation supply stores.
SUPPLIES
A--Valve Installation
Three brass 3/4-inch anti-siphon valves with union fittings (use plastic valves if cost is a concern).
Three 3/4-inch threaded, galvanized steel “T” fittings.
Three 3/4-inch threaded, galvanized 90-degree elbow fittings.
Three 3/4-inch PVC elbows, slip-fit to threaded.
Assorted 3/4-inch galvanized pipe, threaded both ends (three pieces, 2 to 3 inches long; three pieces, 3 to 4 inches; three pieces, 5 to 6 inches; three pieces, 12 to 14 inches, and one piece long enough to drop from water supply outlet to the ground).
B--Sprinkler Head Installation
Four brass quarter-circle pop-up sprinkler heads.
Six brass half-circle pop-up sprinkler heads.
Two full-circle pop-up sprinkler heads.
12 threaded, 1/2-inch plastic risers (height depends on depth of trench and type of sprinkler head used).
Six 3/4-inch slip fit by 1/2-inch threaded plastic “T” fittings for in-line heads.
Six 3/4-inch slip by 1/2-inch threaded plastic elbow fittings for pipe-end heads.
C--Water Lines
Three 3/4-inch slip plastic “T” fittings.
Four 3/4-inch slip plastic elbows.
PVC primer, 8 ounces.
PVC glue, 8 ounces.
170 feet of class 125 (thin wall) PVC pipe.
(Use thicker Schedule 40 pipe if any lines will be under constant pressure. For instance, if you use plastic valves, the pipes delivering water to them are under pressure.)
