The Root of The Problem: How Trees Affect our Sewers

How do tree roots grow, and how do they impact our sewer systems?

As communities have urbanized and densified, increased development has surrounded our trees in a concrete jungle. Especially in urban environments, tree roots, specifically tap roots, must grow deeper into the soil to find water and food.

These roots travel underground like an unorganized highway system as they compete with other vegetation to find the best resources for survival. Roots can grow for hundreds of feet looking for water and nutrients. As the roots grow and expand over time, they ultimately find our underground infrastructure and can grow in and/or around it.

Our sewer pipes are like magnets to tree roots because they contain moisture, oxygen, and food. Initially drawn to the condensation around the pipe, once a root finds opportunities for egress into the pipe, the life cycle of the infrastructure begins to degrade rapidly. The damage will typically continue to get worse as the roots grow and expand.

If untreated, pipes can become blocked completely by tree roots, causing sewage to gush out of manholes and/or flow up a customer’s lateral lines and into homes and businesses. Untreated sewage released by American cities into waterways amounts to more than 860 billion gallons of polluted water each year according to The American Rivers organization.

How do you find roots and prevent them?

During the design of residential, commercial, and industrial developments, the best way to prevent roots from growing into sewer pipes is to install the pipes in areas that are not prone to tree growth, especially avoiding the path of right-of-ways. If your plumber has identified a problem with trees growing into your sewer line, you should try to resolve the root cause of the problem which might mean calling an arborist along with repairing the pipe itself.

Additionally, here are some other options that plumbers and municipal utilities use:

The hydraulic root cutter is the most prevalent method for removing tree roots from a sewer system. This tool is used to cut and remove the roots from the sewer system.  Typically, a high-pressure water nozzle, connected to a combination sewer jetter truck, runs up the sewer pipe and removes the tree roots. The operator can control the power and direction of the cutter, using a joystick to cut through the root system. This tool is effective but takes time and effort to remove all the roots from your sewer system. Additionally, cutting or pruning back the tree roots inside the pipe stimulates growth hormones which can encourage the tree roots to grow back even faster.

Herbicides can be used to coat the inside of pipes to kill and prevent continued root growth. A root control program reduces recurring root growth and increases the life cycle of the sewer pipe by keeping the roots from further damaging the pipes.  It also has the advantage of reducing the frequency of root cutting.

Using a cured-in-place pipe lining (CIPP) you can slow, and in some situations completely stop, roots. If you’re using CIPP to stop tree roots from growing into your sewer system, it would be highly recommended to CIPP line the entire pipe and the laterals to the home to completely prevent roots from entering again. The cost to do this work can be very high and requires a talented and specialized contractor, but it does create a more permanent fix.

Using either a robotic CCTV camera or a “push” camera can be a highly effective way to identify root growth in pipes. However, it can be very time-consuming, requires expensive equipment and there is a possibility of the equipment getting stuck in the pipe.  Due to these constraints, most municipalities struggle to visually evaluate their sewer collection system on anything less than a 10-year cycle. Since tree roots can block a pipe over months and not years, depending on the environmental conditions, CCTV inspection frequencies often do not match the inspection needs of the system operator.

One of the most cost-effective and environmentally friendly ways to find tree roots is to programmatically use the Sewer Line Rapid Assessment Tool (SL-RAT^®) by InfoSense, Inc. The SL-RAT is a low-cost, low-resolution method for identifying blockages. After scanning with the SL-RAT, local government utilities can better deploy other assets, such as CCTV, root cutters, or CIPP solutions to the right pipe at the right time.

What is Tree City USA?

In conclusion, trees bring many benefits to our communities, bringing a sense of fresh air, shade, stormwater management, and beauty while helping reduce the impact of climate change. Overall, tree canopies are assets to our communities that should be encouraged and protected. However, the roots need a place to survive. A lack of design consideration and the growth of trees on top of sewer pipes can create messy basement backups in homes and sewer overflows that contaminate our waterways.

Tree City USA is a combined effort from concerned citizens, volunteers, visionary mayors, elected officials, and urban foresters, that works to benefit communities with a qualified tree-care plan. The only way to truly put an end to tree root destruction is to change our construction specification documents by improving our design, planning, and workmanship. We will never fully prevent roots from causing problems in pipes but can minimize this negative impact by improving our construction quality and preventative maintenance practices to significantly reduce the occurrence of these issues.