Overview: Simple system, easy fixes
An automatic lawn irrigation system is the best way to keep your lawn looking fresh and green. Correctly designed and programmed, it'll deliver the right amount of water to your yard— no more moving the sprinkler! But like any other system, it occasionally breaks down or requires maintenance.
The good news is you can handle 90 percent of the repairs yourself, even without in-depth knowledge of the system. We'll show you how to identify and fix the most common problems. Calling in a professional could cost at least $100, even for a simple problem you can fix yourself in 10 minutes.
Don't be intimidated by the prospect of working on a system that involves both plumbing and electricity. The pipes are plastic and much simpler to repair than the plumbing in your house. The electrical lines are low voltage, so they're not hazardous. You don't need special skills to make the repairs, but you'll need a multimeter to diagnose electrical problems.
Figure A: How a Sprinkler System Works
The controller sends a signal to the control valves in the control valve box. The valves open, sending water through the underground water line, which causes the sprinkler heads to pop up and spray.
Sprinkler heads not working? Solution 1: Replace the heads
Replace a sprinkler head
Dig around the sprinkler head to expose the riser. Unscrew the broken sprinkler head from the riser. Install the new head, turning it tight with your hands.
Broken sprinkler heads are easy to identify. Simply look for cracked or broken plastic casing on the heads, heads that don't pop up, or water that sprays wildly or not at all. It's common to find the top of the head completely broken off. This typically happens to heads that are set too high and are run over by vehicles or hit by lawn mowers.
Replacing the head is one of the simplest fixes. Replacement heads are available at home centers and online. Be sure to buy the same type of head that you're replacing.
To change a broken head, turn off the system and dig a 2-ft.-diameter hole around the head. Using a square shovel, slice the sod into easy-to-remove pieces. Set the sod on a tarp so you can set it back into place at the end of the job.
Dig down to the “riser” (the vertical pipe that branches off the main line) which is connected to the sprinkler head. Dig with a light touch to avoid damaging the plastic water line, which is 8 to 12 in. underground.
Turn the head counterclockwise to remove it from the riser. While the head is off, take care not to spill dirt into the riser. Sprinkler heads are installed only hand-tight, but after being in the ground for several years, they may require the use of wrenches to unscrew. If the head doesn't turn easily, hold the riser with slip joint pliers to keep it from twisting loose from the fittings below.
Attach the new sprinkler head by placing it on the riser and turning it hand-tight (photo). Don't use Teflon tape or joint compound on the riser threads. Sprinkler heads are factory tested to make sure they work. As a result, they're often packaged still wet, so don't be surprised to see water in a new head.
Before filling in the hole and replacing the sod, set the desired sprinkler pattern (see “Reset the Spray Pattern,” below).
Caution: Before you start digging to access the underground water lines, electrical wires or spray heads, dial 811 to have your underground utility lines identified and marked.
Sprinkler heads not working? Solution 2: Clean and reset heads
Photo 1: Unscrew the top
Disassemble the sprinkler head by unscrewing the top from the canister. Rinse away soil and debris in a bucket of water.
Photo 2: Clean the screen basket
Remove the screen basket from the bottom of the head, then clean it with water.
Photo 3: Adjust the spray
Adjust the watering range of the sprinkler head before installing it. Place the head in the canister so the nozzle is at the edge of the area to be watered. Make final adjustments with the water running.
Dirt sometimes gets inside sprinkler heads, causing them to clog up. Clogged heads may rise but fail to spray, not lower after watering, or produce an erratic spray pattern.
To clean the head, dig it out and remove it from the Riser (Photo above). Take the head apart by holding the bottom of the canister and turning the top of the head counterclockwise. Once it's unscrewed, lift it out of the canister (Photo 1).
Remove the plastic screen basket, which serves as a filter, at the base of the head. If you can't pop the basket out with your fingers, pry it out with a flat-head screwdriver or pull it free with a pliers. Rinse the basket in a bucket of clean water, washing out the debris (Photo 2). Clean the rest of the sprinkler head by rinsing it with water. Replace the head on the riser. If it still doesn't work, replace it with a new head. Note: In areas of the country that experience freezing temperatures, polyethylene (poly) pipe is used for the irrigation water lines. PVC pipe is used in areas that don't freeze.
Reset the spray pattern
When putting on a new sprinkler head or using the same head after cleaning, you may need to adjust it to water a specific area. Adjustment methods vary. You can adjust some head types by turning a slot at the top with a screwdriver. Others require a special key that you insert into the head and turn (Photo 3). Some heads also allow you to adjust the spray pattern by turning a tiny screw located next to the nozzle.
Adjust the heads before installing them, then fine-tune them once they're in place with the sprinkler running. First, turn the top clockwise until it stops. That nozzle location is the starting point (the head will turn counterclockwise from there). Adjust the head to set the watering rotation anywhere from 40 degrees to 360 degrees counterclockwise from the starting point. Set the head in the canister. Standing behind the head, align the nozzle with the right edge of the area you want to water, such as along a driveway. Tighten the head in the canister. Carefully backfill the hole and replace the sod.
Turn on the sprinklers at the controller. Allow the head to make a few rotations, then make additional adjustments while the system is running.
Low water pressure? Solution 1: Turn on valves at backflow device
Check the valves
Check the valves on the backflow device to make sure they're open. Turn the valve on the horizontal pipe first, then the vertical pipe valve.
Low water pressure will result in the sprinkler heads barely shooting water. In extreme cases, many of the heads won't even pop up. Start with the easiest solution. Make sure the valves at the backflow device are fully open. The backflow device is located above ground, with the valve at least 12 in. above the highest sprinkler head in the yard. Most backflow devices have a valve on the horizontal and vertical pipes. Turn the valves to their open positions as shown. The valve is open when the handle is parallel with the pipe.
Low water pressure? Solution 2: Find and repair leaks
Photo 1: Install a slip coupling
Cut out the damaged section of line and replace it with a slip coupling. Secure the coupling with band clamps.
Photo 2: Close-up of slip coupling
A slip coupling easily expands and contracts to replace a damaged section of line.
Then check for leaks in the water line. Look for a series of sprinkler heads that aren't watering properly. The water line problem is always located between the last working head and the first nonworking head.
Look for signs of leaking water, such as water bubbling up from the soil when the sprinklers are running, a depression in the ground, or a very wet area. If you find running water, follow the water to the highest point to find the source.
Once you locate the approximate leak site, dig straight down to the water line. Then enlarge the hole along the line, following the flow of the leaking water until you find the break or crack. Before making the repair, make sure the system is turned off at the controller.
Use a slip coupling to repair the leak. This special coupling contracts to make insertion easy. Find these couplings and other repair parts at irrigation supply stores.
To fix the leak, use a hacksaw to cut out a 4-in. section of line at the leak. Place a clamp on one of the line ends, insert the coupling, then tighten the clamp.
Place a clamp on the second pipe end, expand the coupling while inserting the nipple into the pipe, then tighten the clamp. Backfill the hole with dirt and replace the sod.
Low water pressure? Solution 3: Repair crushed pipes
Photo 1: Crushed pipe
Tree roots can grow around a pipe and squeeze it closed after several years.
Photo 2: Splice in new pipe
Cut out the damaged section of line. Replace it with a new section of line, making connections with standard couplings and band clamps.
If you can't locate a leak, the water line may be crushed or obstructed. Sometimes, roots wrap around the line and squeeze it closed over the course of several years (photo 1). Or vehicles may have compressed the soil and collapsed the line. These problems are harder to find and often require a lot of digging. Again, look for the problem after the last working head. Dig along the water line until you find the damaged section. If the line runs near a tree, start your digging there.
Once you locate the damaged section, cut it out with a hacksaw. If the line was damaged by tree roots, reroute the line by digging a new trench away from the tree.
Cut a new section of pipe to replace the damaged one. Then replace the section of pipe, connecting it at each end with regular couplings and band clamps (photo 2).
Zone not working? Solution 1: Check for voltage to the bad zone
Check for low voltage
Check the voltage to the nonworking zone using a multimeter. Touch the leads to the common terminal and zone terminal. If the voltage is too low, replace the controller.
Your watering system is divided into a series of zones. Each zone has an electrically activated valve that controls the heads for a designated area.
Generally, if you have a zone that's not turning on, you have an electrical problem. To solve the problem, make sure the zone wires are firmly attached to the terminals in the controller, the transformer is plugged in, and the circuit breaker at the main panel is on.
Next, test for voltage to the nonworking zone, using a multimeter (at home centers and hardware stores). Turn on the nonworking zone at the controller. Turn the multimeter dial to voltage and place one lead on the common terminal (marked “c” or “com”). Place the other lead on the terminal of the zone that's not working (photo left). It doesn't matter which lead goes to which terminal.
Refer to your owner's manual to see whether the voltage reading falls within the required range (usually 24 to 28 volts). If it doesn't, the controller needs to be replaced. (If you don't get any voltage reading, see “Check Fuse and Transformer,” below.)
Fortunately, controllers rarely go bad unless struck by lightning. New ones start at $175 and can cost upward of $400. Replace a damaged controller with the same brand and model as you currently have. To replace it, label each wire that's connected to the controller with a piece of tape. Unhook the wires, then attach them to the new controller in the same sequence.
Zone not working? Solution 2: Check fuse and transformer
Test the transformer
Test the transformer voltage by placing the multimeter leads on the transformer terminals marked “24 vac” with the transformer plugged in. If the reading is less than 22, replace the transformer.
If no zones will turn on, first turn the controller to the manual setting to see if the system will run. If it turns on manually, the controller is good but the rain sensor may be stopping the automatic programmed watering, which is what it's designed to do.
Rain sensors conserve water by preventing the system from running when the ground is already saturated and doesn't need additional watering. Some states require rain sensors on all new systems. (Your rain sensor is bad if the system runs when the ground is already wet.)
If the system doesn't run in the manual position, check the controller for power. If it has a fuse, make sure it's not blown. Or, if it has a circuit breaker reset button, press the button, then try the system again. If the system is plugged into a GFCI receptacle, press the GFCI reset button.
If it still doesn't turn on, make sure the outlet that the power transformer is plugged into is working by plugging in a power tool. If it's working, plug the transformer back in, turn the system off and test the transformer for voltage. Using a multimeter, place a lead on each of the two transformer terminals. It doesn't matter which lead goes to which terminal.
The transformer terminals are marked “24 vac.” A 24-voltage transformer should normally test between 24 and 28 volts. If the voltage falls below the manufacturer's range, replace the transformer. Simply unscrew the terminals that hold the two transformer wires in the controller and remove the transformer (photo). Insert the wires on the new transformer through the designated opening in the controller. Attach the wires to the controller terminals marked “24 vac” by placing the wire ends under the screws, then tightening them.
Zone not working? Solution 3: Replace defective valve
Photo 1: Replace the solenoid
Disconnect the wires and unscrew the defective solenoid from the control valve. Insert a new one and turn it until it's finger-tight.
Photo 2: Reconnect the wires
Connect the two wires on the new solenoid to the common wire and a field wire, using waterproof connectors.
Photo 2A: Waterproof connectors
Special connectors are filled with silicone to make the connections waterproof.
If the controller, fuse and transformer check out OK, test the resistance “ohms” between the common terminal and the nonworking zone. Turn off the system, turn the multimeter to test for ohms (the omega symbol), and place the leads on the common terminal and zone terminal, just as you did to test for voltage.
Compare the ohms reading with the range listed in your owner's manual (usually 20 to 60 ohms). If the ohms fall below the required amount, the switch (solenoid) that operates the control valve for that zone is defective and needs to be replaced. The defective solenoid will be connected to the same color wire as the zone wire at the controller. (If the reading is too high, see “Repair Damaged Wires” below.)
Control valves are typically grouped with three to six valves in one box (Photo 1). The boxes are located in the ground with a cover that simply lifts off. They can be located anywhere in the yard but are usually close to the main water supply.
Although valves themselves rarely need to be replaced, solenoids do occasionally fail. Replacing them is quick and easy. Be sure the controller is in the off position (you don't need to shut off the power) and the water valves on the backflow device are turned off. Inside the control valve box, remove the wire connectors and disconnect the two wires on the defective solenoid from the common and field wires. Turn the solenoid counterclockwise to unscrew it from the valve (Photo 1). Water will slowly seep out of the valve opening, even with the water turned off.
Place a new solenoid in the valve and turn it until it's finger-tight. Twist the ends of the new solenoid wires onto the same common and field wires that the old solenoid was attached to (Photo 2). It doesn't matter which solenoid wire goes to the common and which one goes to the field wire. Twist a new waterproof wire connector over each connection (Photo 2). To make waterproof connections, use a silicone-filled “direct bury” connector (Photo 2A), available at home centers.
Repair damaged wires If the ohms reading between the common terminal and nonworking zone terminal is too high (it's sometimes an infinity reading), the problem is a severed or bad wire to the control valve. If only one zone isn't working, the field wire is damaged. If none of the zones in a control valve box is working, the common wire is damaged, although the field wires could also be bad.
To find a bad wire, bypass each in turn by temporarily substituting a 14-gauge wire for the original that you run above ground. Make the wire connections with the controller turned off. Then turn the controller back on. Test the field wire first. If the zone turns on, the old field wire is bad. Replace it with an 18-gauge wire rated for underground burial. Bury the wire at least 8 in. underground. Follow the same procedure to test the common wire.
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- 4-in-1 screwdriver
- Slip joint pliers
- Wire stripper/cutter
Required Materials for this Project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.
- Band clamps
- Replacement heads and other parts
- Tubing repair parts
- Waterproof wire connectors