Pipes can be cracked in a number of ways. Tree roots are a common source of obstruction, particularly in leafy suburbs where pipes can be choked by clumps of tree roots, resulting in large overflows of stormwater.
The Gippsland Water paper, Trees and Your Pipes shows the extensive impact of tree root intrusion.
“Water and sewer mains that service your property are often the primary target of tree roots - within a very short space of time they can begin causing problems for you and Gippsland Water.
“Some tree roots have been found to travel up to 30 metres away from their tree base. Once a tree root finds its way into the water or sewer system, the roots begin growing quickly as they have found a constant source of water and nutrients. This enables them to spread long distances within a pipe network, reducing flow and eventually causing blockages and major pipe damage.”
Some pipe materials are more resistant to root intrusion than others. Vitrified clay pipe is easily penetrated and damaged by tree roots. Concrete pipes also allow root intrusions.
PVC pipe is more resistant to root intrusion because it has fewer joints. Because of their flexibility, the tightly fitting PVC joints are less likely to leak as a result of settlement of backfill around the pipe.
The Australian CSIRO and Iplex Pipelines conducted trials comparing the resistance of clay, concrete and PVC pipe joints to tree root penetration under accelerated conditions over 32 months. The report concluded that:
“The performance of the Fibre Reinforced Concrete (FRC) joints was poor compared with PVC but not quite as bad as Vitrified Clay (VC) Pipes. It was concluded that whilst surface roughness, porosity and design play a part, the pH of the pipe material is also a factor.
As a consequence of these accelerated root intrusion tests it was concluded that PVC elastomeric seal joints markedly outperformed FRC and VC pipe joints. ”