Trees are a much-loved part of our landscape both in the countryside and in towns and cities. However, there is often concern about the presence of trees, especially in urban areas.
Property owners often blame them for causing damage to buildings, walls, footpaths, roads, and underground utilities, especially drainage pipes.
However, there is a lot of misunderstanding about the impact trees can have – and cannot have – on built structures and underground pipes.
That is why UKDN Waterflow (LG) Ltd has prepared a White Paper: Trees – Getting To The Root Of The Issue.
It accurately details how trees interact with drainage systems, what property owners and managers can do about the issue, and future trends in managing trees close to drains and sewers.
The White Paper’s Author, UKDN Waterflow (LG) Director Richard Leigh, said: “Tree roots do cause problems in drain and sewer systems. We’re are continuously responding to blockages caused by root ingress into underground pipes.
“However, research shows that trees roots don’t cause initial damage to drains and sewers. Instead, they take advantage of cracks and gaps in pipe joints to get into pipes in their search for water.”
Tree roots – impact on drainage systems
Around 4 per cent of all drainage investigation and repair jobs UKDN Waterflow (LG) is called out to involved tree root infestation of pipes.
Once tree roots have gained entry into pipes they can have a significant impact on its water carrying efficiency.
They can build up significant density in long lengths of pipe, then during heavy rain water backs up and causes flooding. Roots also combine with other materials, such as fats, oils, and grease, sanitary products, and wet wipes to make sewage and pipe blockages worse.
Clay pipes as particularly prone to root ingress, due to gaps in the joints between each section of pipe.
However, modern plastic pipe systems are also affected, and there is research that indicates rubber seals that connect plastic piping are prone to failure under pressure from tree roots.
Future risks – drought and climate change
In the White Paper, Richard Leigh warns that there is a growing need to factor in climate change to tree and drainage management.
In California, USA, efforts to conserve water during droughts have had unforeseen consequences.
Ground movement caused by soil shrinkage has increased pipe damage, increasing the risk of tree root infiltration. As consumers have responded to calls to save water, lower water flows have led to more pipe blockages.
Richard Leigh said: “In the UK, more volatile weather and increased tree root infiltration could combine to increase sewer flooding risks. Changing weather patterns are already encouraging the planting of more exotic tree species.”
In countries like Australia, species include fig trees, rubber plants, camphor laurel, and large gum trees. All are considered to pose an extreme or very high risk of sewer pipe infiltration.
Overcoming tree-related drainage problems
The best way to guard against tree root ingress is to put in place a rigorous planned and preventative maintenance (PPM) programme.
This will identify pipes that are most at risk and catch tree root ingress at an early stage. Key elements of a PPM include:
- Review tree planting plans and avoid species that have particularly vigorous root systems, such as willow, plane, popular, and maple.
- Carrying our regular CCTV drainage surveys to check for defects and signs of root ingress
- Mapping drainage systems to support effective SuDS planning and tree planting
- Keeping pipes clean through water jetting, to prevent a build-up of silt and other nutrients, and water pooling, that can encourage root growth
- Removing tree roots with the most appropriate, cost-effective no-dig method. This may involve high pressure water jetting, electro-mechanical cutting, or robotic cutting.
Pipes that are most at risk of tree root infiltration can also be protected by the installation of a glass reinforced plastic liner, creating a strong barrier to roots.
Richard Leigh said: “It is essential to seek the right expert advice about the potential impact of trees on underground assets. There is considerable misunderstanding on the topic. A practical response based on facts will protect assets and reduce costs into the future.”
For more information, about root ingress and the impacts that tree roots can have on our drainage systems please download a copy of our white paper document, Drain maintenance: getting to the root of the issue.