Taking Care of Drip Distribution Systems

Maintenance is important for drip dispersal systems, especially in areas where rodents are prone to burrow into valve boxes and chew through driplines

Taking Care of Drip Distribution Systems

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A drip dispersal system is a small-diameter pressurized effluent distribution system that can deliver small, precise doses of effluent to the soil surrounding the drip distribution piping. Drip dispersal works on the same basic principles as any other soil-based treatment system: filtering and bacterial decomposition of the effluent. However, the method of application of the effluent to the soil is different. The goal in a drip distribution system is to distribute the effluent evenly over a large area, so no single location receives excess effluent.

A drip distribution system has four parts: a pretreatment device either with or without advanced treatment, a pump tank, a filtering/flushing device and the distribution system. 

All drip systems will have plugging problems without a good filtering system. The filtering system depends on the drip tubing and the manufacturer’s recommendations. Some drip systems require advanced pretreatment, but others have been put in with only a septic tank. The type of pretreatment will in part determine the type of filter necessary. 

A high-head pump is required for even application of the effluent to the soil. Pump selection and installation follows typical onsite treatment system design practices. The filters in drip systems remove all particles larger than 100 microns. Some filters have automatic cleaning systems. Flushing capacity and the total dynamic head are two important design parameters to ensure that effluent passes through the emitters in the tubing. Even with excellent filtration, algal growth in the tubing can cause plugging. Flushing the system removes the growth and minimizes plugging. 

Typical dripline installations are 6 to 12 inches deep, have emitters spaced 2 feet apart and are installed on 2-foot centers (with increased separations on sloped sites). Distribution networks are often laid out with the lines running parallel to one another, but due to its flexibility, dripline can be installed to accommodate irregularly shaped sites and to run parallel to contours on sloped sites. The 2-foot spacing is convenient for installation and has been used in many areas as a basis of drip distribution system sizing. 

Operation and maintenance

Primary treatment tanks and pump tanks should be inspected routinely and maintained when necessary. Recommended maintenance tasks for the drip system depend on the manufacturer and specific components of the system. The manufacturer should be consulted and maintenance performed in accordance with the manufacturer’s recommendations. 

Inspections of the drip system components should be performed at least twice every year. Maintenance of a drip distribution system is similar to maintaining other systems. The tubing and emitters themselves are designed to self-clean, but will still need periodic cleaning, even though they have the automatic self-flushing feature.

Service should include:

  • Cleaning the filters
  • Checking the system to ensure flush and alarm systems are functioning properly
  • Checking flush valves and vacuum release valves and cleaning if necessary
  • Checking pressure-reducing valves to see if cleaning is needed
  • Ensuring that dose volumes registered on the water meter are acceptable in accordance with the system design dose
  • Checking pump discharge capacity
  • Ensuring that wet or damp spots do not appear on the surface of the distribution field

Rodents are active in some areas and can damage drip system components. Gophers have been reported to eat through driplines and burrow into valve boxes and other enclosures, where they can damage components or simply fill the valve box up with soil.

One dripline manufacturer reports that rodents will not burrow toward a dripline when the round is kept continuously moist (one reason for high-frequency dosing). This still could pose a problem during system dormancy — when a drip system is charged and tested and then left out of service for a period of time, such as with seasonable usage, or where a system has been in continuous use but is temporarily shut down during a family vacation. Ideally, a drip system should be tested shortly before it is placed into continuous service. 

Another means of discouraging rodents is to add enough butyric acid to the pump chamber to achieve a 2 ppm solution. Butyric acid is the substance that gives spoiled butter its rancid smell. This substance is relatively harmless but creates an unpleasant odor. 

Possible ways to prevent rodents from burrowing into valve boxes are to line the bottom of the valve box with bricks, drain rock, or other hard material to create a barrier to digging, or to sprinkle butyric acid or powdered boric acid at the bottom of the enclosure, creating an unpleasant odor. Avoid sprinkling anything corrosive on wires or other drip components. 

About the author
Sara Heger, Ph.D., is a researcher and educator in the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota, where she also earned her degrees in agricultural and biosystems engineering and water resource science. She presents at many local and national training events regarding the design, installation and management of septic systems and related research. Heger is the president elect of the National Onsite Wastewater Recycling Association, and she serves on the NSF International Committee on Wastewater Treatment Systems. Ask Heger questions about septic system design, installation, maintenance and operation by sending an email to kim.peterson@colepublishing.com.


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