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Drip System Maintenance and Troubleshooting

The Tomato Magazine
October 2005

By Mark Burgess, CID

Introduction
Today, most of the vegetable crops grown in the Southeast are under drip irrigation systems. The most common type of drip product being used is a thin walled (6, 8 or 10 mil) drip tape manufactured specifically for agricultural use out of a black polyethylene plastic material. While these systems provide for very efficient and simple irrigation, they present the grower with an additional challenge. Like any other piece of farm equipment, they have to be maintained. Without proper maintenance, systems can become clogged, efficiencies lost, failures can occur and the crop can be lost. This article is intended to provide the grower with a basic understanding of maintenance techniques needed for successful crop irrigation using a tape system.

Water Quality
When planning to use a tape system, one of the first recommendations is to test the water being used for it’s suitability for drip irrigation. This is a must. A simple water test can help to prevent serious problems by identifying ingredients in the water supply that may require special treatment. It is better to find out ahead of time than to install a system and experience a failure due to clogging because something in the water went untreated. In many cases, when this occurs, the tape has to be replaced and growers have to spend money for new tape and additional labor.

The University of Florida Cooperative Extension Service provides a water analysis service. Contact your county agent for information and request that an analysis be done to determine the water’s suitability for drip irrigation. Table 1 rates plugging hazards for elements found in water based upon concentrations. If a water analysis indicates a moderate rating, special treatment considerations may be needed; if the rating is severe, use of a special treatment is required. Irrigation dealers should be able to recommend a water treatment specialist with the expertise to drip system water when whenever a possible problem is identified.

Design For Maintenance
After having your water analyzed, the next step is to have the system properly designed. The system should be capable of being easily maintained and include some additional components which will be helpful and, in some cases, necessary. The design should include a filter that will provide the best filtration possible for the available water with minimal maintenance.

Other components to consider are a method of injecting chemicals and/or fertilizer, a flow meter, pressure gauges (before and after the filter), isolation valves, flush valves on all sub-main lines and auto-flushing end caps for the lateral ends. By including components in the design, each can be properly sized (when needed); installation costs will often be less than if added to the system at a later date.

These additional components do add to the overall price tag of the system but, when compared to the cost of a potential failure, they more than pay for themselves. If a water analysis has indicated that specialized water treatment is necessary this is the time to incorporate the needed components. Even if specific water treatment is not needed, an injection point needs to be installed for fertigation and/or use of maintenance chemicals. In some cases, portable filter and pump stations are used, and it is important that all needed components be selected and set up for portability.

The design should also provide very specific information about the system important for proper operation and maintenance. The flow rate and operating pressures for each zone are extremely important. This information will be useful in a variety of ways such as determining injection rates for fertilizers, chemicals and water treatment solutions (if needed). Flow rates will also be very helpful in managing the system for proper irrigation. The travel time for each zone is also important. This is an indication of how long it takes water to move from the filter to the farthest point in a zone and is helpful in determining how long to perform some maintenance and fertigation practices.

Maintaining the System
One of the first maintenance tasks to perform on a newly installed system is to be sure the system is thoroughly flushed before actually irrigating. This initial flushing helps to remove any soil and other debris that may have gotten into the lines during installation. After flushing, it is important that the actual flow rates are recorded for each zone at specific operating pressures. This information becomes a benchmark reading for comparisons during the growing season.

It is also a good idea to measure pressures at the beginning and ends of laterals in each zone, again to establish a benchmark which will be useful later. These pressures can be taken using a 0-20 or 0-50 psi liquid filled pressure gauge, adapted for this by using standard tape fittings and/or other fittings that make this an easy task. If a water treatment method of chemical injection is being used, the injection pump or device needs to be calibrated for the actual flow measurements in order to make efficient use of the chemicals and obtain the proper treatment.

During the growing season, the system should be checked on a regular basis. Some of the recommended items to check are listed in Table 2.

This table does not include everything and is a guide to draw attention to some important checks that can help to identify possible problems before they become serious. Many checks are common sense and sometimes are taken for granted. If a check identifies a possible problem, steps should be taken quickly to identify specifically what is causing the problem and plans made to resolve it as soon as possible.

Possible Problems
Leaks in any irrigation system are a problem. For drip systems they can result in more than just a loss of water. If an underground pipeline breaks, the system can easily become contaminated with soil and sand resulting in clogging. Anytime a break is found, the system should be shut down, the break repaired and the system again flushed before irrigating. Where the break or leak occurs will determine how much of the system should be flushed. The same is true for the tape lateral itself. If it becomes damaged and has been repaired, the end should be opened and allowed to flush any debris out of the tape.

Filters should be checked on a regular basis. Screen, discs and seals need to be visually inspected for breaks and/or tears. Sand media filters need to be inspected for the correct amount of sand and properly working auto-flush mechanisms, if equipped. Manufacturer recommendations should be followed for emptying and inspecting the internals on sand media filters. The filtration system is the first and most important defense against clogging problems, and care needs to be taken to insure that it is in good condition and operating properly.

The most worrisome problem is tape clogging. Clogging can result from a number of things ranging from sand and sediment in the system to growth of biological matter. In some cases, clogging is the result of a chemical action taking place within the water between elements naturally occurring in the water supply and chemicals and/or fertilizers injected into the system. For example, if a water supply has a high pH and high levels of calcium, the addition of chlorine to control biological growth can result in a precipitant that can clog the tape. A similar problem can result if a fertilizer having a high phosphorus content is added to the same water. This is one of the reasons it is strongly recommended to have a water analysis conducted on the water supply.

Even with the analysis, one has to be very sure that things being injected into the system (fertilizer, chlorine, acids and treatment chemicals) are compatible with the elements in the water such that unwanted chemical reactions do not occur. Understanding this relationship between the water supply and materials to be injected is a very important part of maintaining drip systems. It doesn’t mean you have to be a chemist, just that you should do some research. You should also have the support of a qualified local irrigation distributor who is experienced and knowledgeable with water conditions in the area and who can make recommendations that will help to prevent these types of problems.

The best way to deal with a clogging problem is to prevent it. Refer to Table 2, and if you see any of the indicators that clogging is occurring, identify the cause and perform the necessary treatments. Many growers use a preventive maintenance schedule of adding chlorine, acids and/or other chemicals to systems on a regular basis in order to help prevent problems from biological growth and other contaminants. The materials used, amount and frequency will vary. It is important that what is done will address the possible causes of problems in your system and be compatible with your water supply. Just because it works for the grower next door, doesn’t mean it will work for you. At this time, there is no one material that addresses all of the factors that can cause clogging. You should work with your local extension agent, irrigation distributor and/or water quality specialist in order to develop a program that will best meet your needs.

Summary
Most irrigation system maintenance tasks are common sense and are almost second nature to growers. There are, however, issues involving water quality that require special attention, and it is important that you seek advice from experienced people who are knowledgeable about local conditions. Drip tape is now available through a variety of sources including irrigation distributors, hardware stores, catalog sales, the Internet, growers and other agri-businesses.

With a variety of choices, it is important that you are cautious and work with a supplier that can provide you with good support and service for the products you buy. The cost of drip tape is a very small part of what is spent growing a crop, and while every dollar is important, there are times that an extra dollar or two per acre may well be worth the help available to you if problems occur with the drip system. Proper maintenance will save you money and extend the life of the system while providing for an efficient way to use our water resources for irrigation. Remember, “Prevention is the best medicine.”

© 2006 Columbia Publishing

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