Tree roots in drains and sewer pipes: what a tree society, a city, a university and a council say

This page reports what the official source says. It is not legal advice: ask the office named here. It does not say whether any root has damaged any pipe. The sources describe who maintains a pipe in the places they cover, and the rules differ from one place to the next.

Why roots are found in pipes

The International Society of Arboriculture (ISA) brochure Avoiding Tree and Utility Conflicts says electric, gas, water and sewer lines installed underground can be compromised by tree roots, and that roots commonly spread many times the breadth of the crown. For water and sewer lines it says new pipes made of steel or PVC are generally resistant to root damage, while older cement, clay or cast-iron pipes that have degraded may develop leaks. It says moisture from the leaks attracts roots, which can penetrate and widen the cracks.

The City of Cleveland Urban Forestry memo Treating Defective Sewer and Water Lines for Tree Roots says roots need water and oxygen, and that water escaping from a cracked or broken service line leaves a trail that roots follow. It states that tree roots do not break water or sewer lines, and that removing a tree will not resolve cracked and broken pipes.

The University of Tennessee Extension publication Choosing Sewer Safer Trees says roots grow into sewer pipes because the pipes hold water, nutrients and oxygen. It says how much root invasion happens depends on the condition of the sewer line, the type of tree and the soil, and that the literature it reviews mostly points to making the sewer lines themselves sounder.

Merri-bek City Council, in its leaflet Tree roots, stormwater and sewer pipe damage, says tree roots are usually not the primary cause of failure of underground pipes. It names improper installation, poor maintenance, faulty joints, cracks and ground movement as the more usual causes, says this typically occurs in old earthenware clay pipes, and says it is extremely unlikely that roots will damage intact pipes.

What each source says about whose pipe it is and who looks at it

Source	Whose pipe	Who the source says looks at it
City of Cleveland, Ohio	Each homeowner is responsible for annual maintenance of the sewer lateral, the pipe from the house to the main sewer at the street.	Sewer contractors that perform television inspections of pipes and offer root control options.
Merri-bek City Council, Victoria	In a leaflet written for roots from council-managed trees, the landowner keeps up and replaces the pipes between the property and the legal point of discharge (stormwater) or the connection point (sewer). Beyond that point the pipe belongs to the water authority or the stormwater owner.	A registered plumber first. If digging is needed, the leaflet says to contact the council's Urban Forest team so a council arborist can inspect and prune roots while the pipe is open. It says council will not remove trees because of roots in private pipes.
University of Tennessee Extension	Not addressed.	The local public works department, for the location of sewer lines, drain fields or connection pipes.
ISA	Not addressed.	An ISA Certified Arborist, named elsewhere in its brochures for assessing trees.

The Cleveland memo also names options for pipes with roots in them: clearing with an auger, foaming root killers used to the label, and replacing the service pipe with PVC where the city allows it. It warns against rock salt and copper sulphate because they have been shown to be problematic in streams and sewers. Merri-bek says pipes that keep blocking can be repaired or replaced with PVC, or in some cases relined, and that permits may be needed from the council.

What the sources say about planting near pipes

The University of Tennessee publication says there are no sewer-safe trees, but that small, slow-growing species with less aggressive roots should leave sewer lines safer. It lists large, fast-growing, aggressive-rooted trees such as ash, sweetgum, poplar, willow, linden, tuliptree, sycamore and many maples as not recommended near wastewater pipes, and says trees should be located more than 10 feet (3 m) from sewer lines. The ISA brochure says natural gas operators often keep the area over a pipeline, and 10 feet (3 m) either side, clear of trees. The guide on calling before you dig reports how underground lines are located, and the guide on choosing a tree reports more on planting near utilities.

Where the sources agree

Three of the four sources link roots in pipes to pipes that were already leaking or cracked, and none says a tree has been proved to be the cause in any particular case. For roots and foundations rather than pipes, the guide on tree roots and buildings reports what surveyors and councils say.

Who to call

ISA Find an Arborist: the ISA directory for an arborist who can look at a tree
Call before you dig: the services that locate underground lines in each country
Merri-bek City Council: the Victorian council whose leaflet is reported here; other places have their own water authority or public works office
Consulting arborists by country: the credentials and registers consulting arborists hold in each country