Installing an Underground Sprinkler System: Part 2
Installing an underground sprinkler system is a time consuming operation. Be prepared to spend at least two weekends full time installing it yourself. Although the task may seem daunting, if broken down in to chunks it is very manageable. You have the water inlet tapped in to, have installed the distribution manifold, and now are ready to lay the actual sprinkler system.
Begin your preparation to lay the lines for the sprinkler system by giving the lawn a good soaking a day or two before you begin. This will allow the ground to be much easier to dig in. There are three methods used to install the pipes. They are:
- a pipe puller
- a trencher
- hand digging
A pipe puller is a device that literally "pulls" the pipe through the ground. This method is the most difficult to use. Basically, a knife edge is driven into the ground to a given depth, and the pipe is then pulled through the ground behind it. Most homeowners are not experienced enough to use a pipe puller to their best advantage. A pipe puller with an operator can usually be rented. You would assist the operator in the installation. Plan on spending 80 dollars an hour for this operation. This method is best for lawns that already have an established sod base, because it does the least damage to the lawn.
The second method is a trencher. It basically digs a "V" shaped trench to the depth you wish. Gas operated, it can quickly dig your trenches with the minimum amount of work. It allows you to control depth, and gives a good visual for the actual pipe laying. This method is usually the most recommended.
The third method is to hand dig the trenches. This is the most labor intensive, and it would be very time consuming. If time and physical labor are at issue, then consider using a trencher.
Dig the trenches 6 to 10 inches deep. If the area is flat, have the trench drop at least a quarter of an inch per five feet to facilitate draining of the system during the winter months. Now is the time that your graphic plan of the layout becomes useful. The plan will identify the type of sprinkler head, the placement, and all aspects of the installation. The system will be laid out in circuits, and controlled by the control valves in the distribution manifold, and these valves are activated by the controller that is installed in the garage.
Each circuit is attached to a control valve. This article assumes you are using PVC pipe for the installation. Put an inch of gravel in the bottom of the trenches to insure drainage. Carefully measuring each section, cut the PVC pipe to length with a tubing cutter and place all in the trench. Although you can cut PVC with a hack saw, it requires a holding device, and you are not assured of a clean straight cut, essential in the mating of the joints. Burr the cut edge, and using emery paper, take the gloss off the pipe. Use PVC cleaner to clean the pipe before installation. Attach each length, according to plan, to the PVC threaded tee that will hold the riser for the sprinkler head. Dry install the riser to the tee. As you attach each tee, use a carpenter's square to insure the riser is 90 degrees to the ground. When attaching each joint, first insure the fit is correct and that the pipe bottoms out in the joint. Mark the PVC pipe with a felt tip marker at the required depth, and draw an alignment line on both pipe and joint. Apply PVC solvent to the pipe and tee, and press them together. When doing so, set the alignment mark about two inches off, and turn the pipe to align the marks. This insures a full coating of the solvent. Check the mark for depth to insure that it is fully seated. Work quickly - the PVC solvent sets up in about 30 seconds. When all tees are in place, and all pipe connected, allow the installation to cure for several hours before final installation of the risers.
When installing the risers, measure carefully to insure that the height is correct for the type of sprinkler head installed. The sprinkler heads should extend about 5/8-inch above the ground before sod is laid and should be level with the sod root base afterward. If installing in an established lawn, it is simply a matter of insuring that the sprinkler head is level with the existing sod base. Once the riser has been installed, attach the sprinkler head. Allow the completed system to cure overnight before turning on the water.
Each circuit is controlled by the controller in the garage. These controllers operate the circuit valves with 24 V AC, a voltage that will not harm you. When water is applied to the system, and it is insured that there are no leaks, set up the controller to energize each circuit in stages. Remember, the average home does not generate enough water pressure to run the entire system. Stagger the times each circuit engages using the timer system on the controller. Depending on the price paid for the controller, almost any combination of circuits can be controlled.
An average installation on a small yard is currently around 900 dollars. To have it done by a professional service would cost approximately 1,600 dollars. Do it yourself is definitely the way to go if expense is a major consideration.