What do you need to know about root ingrowth in sewer pipes?

Sewer and pressure pipelines are dimensioned to ensure reliable supply and disposal. However, if obstructions or deposits are present inside the pipe, their functionality may be compromised. As more material accumulates, this can eventually lead to a complete blockage. Intrusions into the pipe cross-section affect flow behaviour, reduce flow velocity, and can, especially during heavy rainfall, trigger backwater in the sewer system. Obstacles can include crossing pipelines, protruding pipe connections, fallen objects, and also root intrusion. In the water and wastewater industry, this term refers to the penetration of root systems into pipes and sewers. Sewer systems in particular offer ideal conditions for roots to spread.

In this blog post, we take a closer look at root intrusion in pipelines. What are the underlying causes? What are the challenges and how can MOWOTAS pipe cleaning products help address the issue?

Root ingrowth - where does it come from?

As urbanisation progresses, natural spaces within cities are becoming increasingly scarce. In search of water, roots can infiltrate underground infrastructure and cause significant damage. It is not uncommon for tree roots to extend up to 20 metres underground in pursuit of vital resources.

Root intrusion can block sewers and even lift masonry structures. There are documented cases where roots have penetrated through walls into buildings and reached toilet cisterns in search of water. Often unnoticed above ground, roots find their way towards nearby water sources and can cause substantial damage in the process. Root intrusion has now become a widespread issue. It typically occurs due to faulty or leaking pipe joints, poor soil compaction, or erosion around the pipeline. Many older pipelines provide ideal conditions for this kind of growth, offering a warm, moist, and nutrient-rich environment.

Expensive damage

The roots are usually only discovered when technical problems occur in the pipe. By then, however, the roots have usually already caused major economic damage. Once a sewer pipe is affected by root ingrowth, it can get to the point where the pipe is completely blocked with roots. At this point at the latest, the water backs up and reaches the house. The pipe now urgently needs to be cleared and the roots milled out.

A sewer with ingrown roots is considered to be leaking and must be repaired. Regardless of whether there is actually a backflow or not. And especially when main drains and sewer pipes are affected, it can be expensive. The risk of sewer damage increases, which in turn brings with it the danger of flooding roads or buildings. In addition, plant material penetrating the sewage pipes damages the outer walls of the pipes, which can lead to leaks or even complete pipe breakage. The consequence of this is not only a problem with the correct discharge of wastewater, which leads to possible backwater on roads or in cellars and buildings, but also the contamination of soil and groundwater.

Damage patterns due to root ingrowth

To prepare for pipe renovation, it is very important to know the type and exact location of the damage as well as its frequency. This is the only way to determine whether individual damaged areas should be repaired or whether the entire pipe should be renovated. For this reason, a sewer TV inspection is usually carried out. The sewer cameras are self-propelled or are pushed or pulled through the pipe. The camera must be positioned in the pipe axis. The camera's evaluation unit consists of a monitor and a computer for processing and recording the images. All important information about the image must be recorded on the monitor:

• Examination location
• Date/time
• Pipe data (material, diameter)
• Damage at the respective location (type of damage, distance, position in the pipe)

Who is liable for the damage?

As a rule, the owner of the tree is liable for the costs incurred as a result of root ingrowth. It is therefore helpful to find out who owns the tree that caused the root ingrowth in the sewer or pipe. This is the only way to get your money back. For this purpose, root DNA samples are taken and compared with the trees in the immediate vicinity.

How to prevent such damage

The best way to avoid damage is to avoid growing trees and shrubs too close to sewer pipes and only use plants that cannot damage pipes. To prevent root ingrowth, damage and the associated costs from occurring in the first place, preventive measures must or should be taken in sewer construction.

Plastic is the most suitable material for sewage pipes as it is durable. Root ingrowth can also be limited by preparing the ground. Roots prefer a moist, oxygen-rich environment that is easy to grow through. If low-porosity backfill materials are used for the sewers and the soil around the pipes is aerated, this is no longer so attractive for plants. Alternatively, root trenches can be created around the pipes.

How do I remove root ingrowth with MOWOTAS products?

If technical problems are caused by tree roots, a specialised company should remove them using appropriate tools, such as chain skidding or root milling. The sewer or infrastructure should be inspected once the roots have been removed. MOWOTAS offers chain extractors, root cutters and a milling robot for root removal. A range of nozzles can also be used to combat root ingrowth. We recommend using the following nozzles for root ingrowth:

• Root Cutter Nozzle
• 3-edge nozzle 1/4" - 1" for stubborn blockages
• Rotary nozzle for clogged and rooted pipes 1/2"-1"

Due to the constant root growth of plants, it may make sense to replace entire sections of pipework in individual cases. Depending on the case, it must be clarified whether repair, renovation or renewal is required. MOWOTAS sleeves or our products for short liner and long liner renovation can be used here:

• Pipe Rehabilitation Sleeves
• Pipe Lining, Seals & Track Rehabilitation Inliners
• Partial Renovation & Short Liner Rehabilitation Products

Camera systems should be used beforehand to analyse root ingrowth in pipes. This is the only way to provide the insurance company with watertight documentation of damage patterns. Take a look at our wide range of pipe inspection cameras.

Would you like to know more about the products you can use to combat root ingrowth? We will be happy to advise you!

Author: Dr. Daniela Brandt || You can find out more about the person who wrote this article on Linkedin.