Nearby trees can wreak havoc on a leaky septic system, but this can be prevented with thorough inspections and an arsenal of root removal techniques
Trees don’t ask for much — soil, water, sunlight. And they provide a wealth of benefits: They improve the air you breathe, cut your energy bills with their shade, provide homes for wildlife, and add beauty.
But for septic systems, the roots from these trees can be one sign of a very big problem. Older pipes made of concrete or clay are the most likely to attract roots, due to leaks. Regular septic system inspection and maintenance can help to keep root intrusions at bay. When inspecting a system, be on the lookout for signs of leaking pipes and components. If you run into the issue frequently, it may be wise to invest in a micro video sewer probe to verify the integrity of the system.
First and foremost, the best solution is to prevent the roots from getting into the tank. No amount of chemical will repair a broken pipe. The sooner seepage or leaks from failing pipes are detected and repaired, the less likely roots are to exploit this vulnerability and gain access to the system. Common points of access are at the inlet, outlet, lid or even through manholes. They can also access the tank through poor pipe connections. When the “weak point” is identified, it should be repaired if possible. There are some tanks where the solution will be replacement of the tank and/or piping.
When extensive root activity is found in pipes and components, the roots will need to be moved. In pipes this typically occurs with a mechanical root-clearing tool. When used with chemicals, roots may be substantially delayed. However, if continuing leaks in the pipes are not addressed by repair or by total replacement of existing concrete or clay pipe with PVC sewer pipe, roots will eventually recur inside the pipes. In many cases, removal of fast-growing trees on the property is also recommended to alleviate recurrent root intrusions.
Planting trees, shrubs and even some ground covers over septic system soil treatment components are causes of septic system problems. Trees, shrubs and some deep-rooting grasses will send out roots that are attracted to the nutrients in wastewater. All of these types of woody vegetation should be kept off the top of the system and ideally be 20-plus feet away depending on the type of vegetation. Trees known for seeking water reservoirs — such as poplar, maple, willow and elm — should be planted at least 50 feet away. A good resource to identify appropriate trees nearby septic components can be found at: extension.tennessee.edu/publications/Documents/SP628.pdf.
If the roots from existing trees are causing problems in the soil treatment system, you can potentially prevent roots from entering the lines by installing root barriers in vertical trenches between the trees and the lines. Plastic panel root barriers are available in various depths up to 24 inches, and can commonly be found where irrigation supplies are available. These geotextiles are impregnated with a long-lasting herbicide that moves a short distance into the soil. To effectively stop tree roots, the barrier should extend from the soil surface to a depth of at least 2 feet. Some roots may still grow under the barrier, but intrusion into the drainfield should be greatly reduced. Install the barrier fabric at least 3 feet from the drainfield so as not to disrupt the system. Allow at least 5 feet (the more the better) between the tree and the root barrier — more if it’s a very large tree. The geotextile barrier should not encircle the tree, as this could prevent it from growing. Instead, run the material the entire length of the drainfield to prevent roots from getting into the field by going around the barrier.
There are many products marketed to clear roots from systems. The most common treatments use copper sulfate and have been shown to be effective in preventing small roots from growing into mature roots. Copper sulfate is an inorganic compound and can kill bacteria, algae, roots, plants, snails and fungi, and is widely used around the world as a pesticide and seed fungicide.
Chemical treatments need to be repeated at regular intervals; therefore, in the long run more direct action will likely be required. The money spent will add up over time and would be better spent repairing the system and preventing the root access. In addition, many of the chemicals on the market contain toxins and contaminants which will eventually enter the ground or nearby surface water. Because these chemicals are sometimes regulated locally, check with your county or state to make sure you are using the product legally and correctly. Fixing the system is a much better solution.
Trees and shrubs add aesthetic beauty to a property, increase value, save on air conditioning and assist in preventing runoff and erosion. They are valuable resources; we just need to be smart about how they can potentially impact septic systems.
For more information on what can be planted over and around an onsite system, read Explore Landscaping Options for the Septic System.
About the author
Sara Heger, Ph.D., is an engineer, researcher and instructor in the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota. She presents at many local and national training events regarding the design, installation and management of septic systems and related research. Heger is education chair of the Minnesota Onsite Wastewater Association (MOWA) and the National Onsite Wastewater Recycling Association (NOWRA), and serves on the NSF International Committee on Wastewater Treatment Systems. Send her questions about septic system maintenance and operation by email to email@example.com.