Research has shown trees can provide up to $7 in annual benefits for every $1 invested in caring for them. Benefits include increased property values, pollution control and energy savings, and they are beautiful! Unfortunately, tree roots can cause problems in septic systems.

Roots are estimated to make up 20 to 40% of the total biomass of trees. Trees have two types of root sizes — coarse and fine. Coarse roots (more than 1/12 inches in diameter) anchor the tree in the soil and transport water from deeper soil horizons. Fine roots (up to 1/12 inches in diameter) uptake water and nutrients. 

The typical rule of thumb has been to keep trees 20 feet or more away from the septic system, but increasing this distance is undoubtedly a good idea for new tree plantings. Trees known for seeking water, such as poplar, maple, willow and elm, should be planted at least 50 feet away from the septic system. Planting smaller ornamental trees nearby is advisable since their roots will be less extensive.

Suppose you live in a part of the U.S. that has experienced drought conditions. In that case, the recommended separation distance between trees and the septic system may not effectively limit the problem as expected. Trees may enhance fine root growth during droughts and form deeper coarse roots to increase water uptake. Trees that have adapted to dry climates tend to have higher root-to-plant ratios, and research shows this happens during severe droughts in non-arid environments. 

WHERE THEY TRAVEL

The first location where tree roots commonly cause problems is the building sewer to the first tank. The critical issue here is determining how the tree root is getting into the pipe and repairing it. A pipe inspection camera can aid in diagnosing this issue. It may be because the pipe is of inferior quality, cracked or otherwise damaged. Be aware that tree roots may crush or lift the pipes, creating a location for debris to catch and freezing to occur.

Proper repair includes cutting out the root entirely and relaying the pipe at the appropriate grade. If the pipe is not up to current standards, the entire pipe from the source to the tank should be replaced. With this repair, you may damage the tree to the point that the tree will die. With high-value trees, check with an arborist if you need clarification.

With tree roots in septic and pump tanks or advanced pretreatment units, the question is the same as solid pipe — how are they getting in? A service provider must remove the roots, and the source for entry must be blocked permanently. Left unchecked, the roots can cause backup into homes due to their aggressive growth.

Tree roots can make their way into and around conventional systems. Growing around the system is not a problem, but the root must be physically removed if it gets into the perforated pipe. The quickest way to deal with this issue is physical means of removal (jets, augers, etc.).

Unless the tree is cut down or the system is replaced in another location, physical removal must be immediately followed with applications of a chemical root killer or installation of a mechanical and/or chemical barrier. Otherwise, the plant regrows those roots vigorously. If a chemical is used, it will be for the system’s life; although the frequency of re-treatment may diminish, the need never goes away.

BUILDING BARRIERS

A mechanical barrier (sometimes called a tree root deflector) is typically made of plastic or metal installed vertically into the soil. It forms a barrier that redirects or restricts the growth of tree roots, preventing them from spreading into unwanted areas. These barriers are designed to direct roots down and away from the septic system component.

Some walls are impregnated with cupric acid or trifluralin to inhibit the growth of all tree roots they encounter. Care should be taken as these chemicals are toxic to humans. Special attention during installation is needed at every joint of either physical or chemical barriers, as roots can easily penetrate and defeat the wall.

During installation, exceptional care must be paid to ensure the extension of the barrier below the maximum depth the roots will penetrate. If you need more clarification on this depth, it is another time to discuss the issue with a local arborist. It would be best to be careful to install them only a short distance from the tree, or it may need more root growth to sustain its height and water/nutrient needs.

Also, depending on your location, the depth of UV penetration may be several inches, so the barrier product must be very resistant to this. If/when the top of the barrier deteriorates or is damaged from traffic/activity, the roots will travel over the top of the barrier and continue to cause problems. 

Trees add aesthetic beauty to a property, increase value, save on air conditioning and assist in preventing runoff and erosion. They are valuable resources; we must consider how they can impact septic systems.