A tree's roots supply it with the water and nutrients it needs to survive. However, as trees mature, so do their roots. In time, these can enter wastewater pipes and damage them, obstructing the flow and eventually causing a blockage. Roots can also displace water pipes causing them to burst.
Root damage from trees can also allow stormwater to enter the pipes. During heavy rain this extra water can overload the wastewater network, causing it to overflow into waterways, streets or even your back yard. This represents a significant environmental and public health risk. There are also financial costs to consider - if the problem occurs in your private wastewater pipes, it's your responsibility to have it fixed.
Avoiding damage to your sewer pipes
The key is to plan ahead. Plant trees as far away from the underground services as possible and plant species that are less likely to cause problems.
Before planting, find out where your wastewater and water pipes are located so that you can stay clear of them. All homeowners should have a plan of their property which shows the location of underground services. Contact the Auckland Council to obtain a copy of your plan. At the same time, check the location of the public wastewater pipe that will run past your property.
Make sure the tree you have chosen is appropriate for where you want to plant it. Your local nursery can help with this or you can consult a gardening guide. It's important to find out how far the tree's roots will travel - they usually extend about one and a half times the distance of the adult plant's branches and up to 1.5 metres deep. Don't plant large, fast-growing trees with vigorous root systems near sewer pipes. If you need to plant vegetation over or near a sewer line, choose shrubs, grasses or small trees with less extensive root systems.