by Phil Robish

The pressure is on the landscape industry. Government agencies and water purveyors alike are watching us carefully to see if we can conserve water. If we can’t govern ourselves, laws and codes will be enacted to ensure that we do.
The other side of the coin is that there is an opportunity to expand your business by offering your customers a much needed service. That service is to schedule regular inspections of turf and landscape sites to make sure all sprinklers are performing efficiently.
During this weekly or monthly inspection, check each zone for excessive wet or dry areas, and make sure the heads are in proper adjustment, i.e., they’re not spraying too far out or too close in.


What to look for

Look for signs of broken risers beneath the sprinklers. Sometimes this is obvious: the riser is completely broken and the unleashed water is creating a traffic-stopping geyser. Sometimes a problem may not be so obvious: a cracked riser will allow water to boil up around the sprinkler and create puddling.
While you are looking for broken risers and pop-up heads that need adjustment, you should also inspect the sprinkler riser wiper seal for flow-by. A very small amount of water emitting past the wiper seal is acceptable (while the system is running). If you see excessive flow-by while a system is operating, it indicates a damaged wiper seal — and the result is wasted water. But if the sprinkler head is leaking constantly, then the head must be repaired or replaced.
Many times people will replace a sprinkler because it leaks between the wiper seal and pop-up stem after the system has turned off. This leakage does not mean there is a problem with the sprinkler, but rather low-head drainage, or a valve that needs maintenance or repair. (If water drains out after the system has been turned off and eventually stops, the valve is fine.)
When you see water
puddling around a
sprinkler, it could be a sign of a cracked riser or
broken swing joint. It will need to be dug up to determine the problem and then replaced.
Photo courtesy: Hunter Industrie

 

Low head drainage

Low head drainage can be reduced or stopped with the use of a check valve. Many sprinkler manufacturers have check valves that can be retrofitted onto their sprinkler heads. Check valves will usually hold back water in a pipe with seven to 10 feet of elevation change.
Poor irrigation coverage can also be a sign of clogged filters or nozzles, and it may be time to clean dirt and debris out of the sprinkler. Sprinkler head filters are generally accessible without having to completely remove the sprinkler from the ground. The filters are located directly under the nozzle or under the pop-up stem.

How to clean clogged nozzles

For spray heads with filters located under the nozzle, hold the pop-up stem and unscrew the nozzle, being careful not to damage either. A damaged nozzle may result in an uneven spray pattern, and a damaged pop-up stem will result in a poorly performing wiper seal. Remove and clean the filter.
Clogged nozzles can be cleaned by flushing with water, or by lightly tapping the nozzle on a firm surface. While the filter is out, turn on the zone and flush out the sprinkler body. Reinstall the filter and nozzle, urn the zone on and recheck for coverage. Make all necessary adjustments to the radius, and if applicable, to the arc as well, to make sure you are covering the area intended to receive water. While the water is on, inspect the other heads on the zone for proper operation.
To clean filters installed under the pop-up stem, unscrew the cap from the body. Be careful that dirt does not fall into the sprinkler body while the riser assembly and cap are removed. The filter can be found on the bottom of the riser assembly. Remove the filter (this may require the use of needle-nose pliers) and flush the filter with water. Before reinstalling the assembly, run a small amount of water through the system to flush any debris caught in the sprinkler body.
It is very important that broken or poorly performing sprinkler heads be replaced as soon as possible. When a specific sprinkler is not operating as designed or if water is flowing freely because of a worn wiper seal, the performance of all the other heads on the zone is affected. Water flowing unchecked past a wiper seal will cause a loss in pressure. When the pressure in the zone drops, the other sprinklers will not perform correctly and will not cover the area required.
Sprinkler manufacturers recommend the use of check valves to prevent low head drainage. Check valves can be retrofitted into sprinkler heads.  
 

Choosing a replacement sprinkler

Once an unsatisfactory sprinkler is identified, replacing it is usually an easy job. When replacing sprinklers, you should use the same type of sprinkler head. There is a wide choice of replacements if you do not want to use the same model type. Most sprinkler manufacturers have nozzle replacement equivalency charts (available from your irrigation distributor) which will cross-reference one sprinkler to another. However, certain guidelines must be followed when making the decision of which sprinkler to buy.
Residential and light commercial sprinklers fit into two basic groups: small area sprinklers and large area sprinklers. Small area sprinklers are usually installed in areas that are 25 feet by 25 feet or smaller. Large area sprinklers are typically found in areas larger than 25 feet by 25 feet. These are not hard lines that are never crossed, but rather quick rules of thumb.
Small area sprinklers are usually fan-type spray heads. Fixed fan spray heads occasionally need to be adjusted and cleaned, but will rarely need replacement unless damaged. These heads are most commonly placed on risers that are 12 to 18 inches above the ground, and are installed away from traffic in shrub areas.
Within the large area sprinkler group, you can choose rotors that are either fixed shrub heads or pop-ups. The large area group includes 3/4-inch inlet sprinklers that will cover between 17 and 50 feet, and one-inch inlet sprinklers that will cover from 40 to 75 feet or more. 
Clogged filters or nozzles will interfere with efficient irrigation coverage. Filters are located directly under the nozzle or under the pop-up stem, and can be removed to clean out the dirt and debris.
Photo courtesy: Hunter Industries		  
 


Precipitation rates

In choosing new sprinklers to replace old models, it is important to realize there are huge differences in precipitation rates (the amount of water applied to a given area). Make sure to replace small area sprinklers with similar small area spray heads, and replace large area sprinklers with large area rotors. Within these two groups you will find sprinklers that deliver the equivalent amount of water for the area covered as the ones you are replacing.
Stated another way, a 17-foot spray head will place about 3-1/2 gpm (gallons per minute) in its area, while a 17-foot rotor will place about 3/4 gpm in the same area. Before you install new sprinklers, check their precipitation rates and determine whether they are appropriate for the area you are planning to irrigate.

Review features and benefits

There are many other reasons for replacing sprinklers, other than worn wiper seals or poorly performing heads. Old brass gravity-style spray heads may not be popping up high enough to clear the grass and ground cover. Pop-up impact heads are noisy, and customers may want them replaced.
Once you have decided to replace sprinklers, review the features and benefits of various manufacturers. Newer closed case gear-driven sprinklers are quieter. These smooth operating sprinklers have lower operating costs because the water is more evenly applied to the landscape, and the heads have fewer exposed moving parts.
Open case rotors can be adjusted to water brown spots closer to the sprinkler, but matched precipitation rates and longer distances of throw are relinquished when the heads are adjusted this way. Pop-up impacts often expose many operating parts to the elements, and allow dirt and debris to enter the case and clog the mechanism.
To clean a filter located under the pop-up stem, unscrew the cap from the body. Remove the filter from the bottom of the riser assembly with needle-nose pliers, and flush the filter with water.
Photo courtesy: Hunter Industries		  

There are many other reasons for replacing sprinklers, other than worn wiper seals or poorly performing heads. Old brass gravity-style spray heads may not be popping up high enough to clear the grass and ground cover. Pop-up impact heads are noisy, and customers may want them replaced.
Once you have decided to replace sprinklers, review the features and benefits of various manufacturers. Newer closed case gear-driven sprinklers are quieter. These smooth operating sprinklers have lower operating costs because the water is more evenly applied to the landscape, and the heads have fewer exposed moving parts.
Open case rotors can be adjusted to water brown spots closer to the sprinkler, but matched precipitation rates and longer distances of throw are relinquished when the heads are adjusted this way. Pop-up impacts often expose many operating parts to the elements, and allow dirt and debris to enter the case and clog the mechanism.

The advantages of current technology

Today’s sprinklers offer the flexibility of interchangeable nozzles, so one type of sprinkler can be used in several applications. Modern sprinkler heads also have high quality, heavy-duty retraction springs, use superior wiper seals, and take advantage of today’s exact engineering standards in the production of sprinkler assemblies and nozzles.
After the decision to upgrade the sprinkler system has been made, and the various features and benefits considered, talk to your local distributor. Find out what kinds of experiences he has had with the manufacturer you are considering, and what type of support and warranty policies the manufacturer provides. You will also want to know how long the product has been successfully performing under all challenging conditions.
Water is an important resource. As landscape professionals, we must do all we can to conserve it.

Editor’s Note: Phil Robisch is education manager at Hunter Industries.

May, 2004