Guarding pipes from Tree Roots

[TOHSEngineer]

I have an existing asbestos cement pipe that I will be planting trees almost directly above. The pipe is old and is estimated to have 3.5' of cover. We plan on planting shallow rooting trees but I would also like to use some sort of root guard for added protection.
Does anyone have any products/practices they could suggest?
Thank you.

 

[cvg]

this sounds like a very bad idea, relocate the pipe or the trees

 

[rconner]

I suspect that most folks reading your inquiry will think first about the risk of roots seeking and penetrating a poor joint, or somehow wrapping around otherwise somehow structurally compromising a brittle pipe material etc. However, I guess depending on exactly what specific chemicals/carriers you are thinking about using in the area, I suspect there could even conceivably be additional concerns. The latest version e.g. of AWWA C400 for asbestos cement water distribution piping that I think was approved on or after 2003 includes all kinds of information with regard to health and regulatory approval aspects of potable water piping, and also includes the following specific passage (that calls out some piping materials by name, including asbestos cement),

"Sec. 4.1 Permeation
The selection of materials is critical for water service and distribution piping in locations where there is likelihood the pipe will be exposed to significant concentrations of pollutants that are comprised of low molecular weight petroleum products or organic solvents or their vapors. Research has documented that pipe materials, such as polyethylene, polybutylene, polyvinyl chloride, and asbestos cement, and elastomers, such as used in jointing gaskets and packing glands, may be subject to permeation by lower molecular weight organic solvents or petroleum products. If a water pipe must pass through such a contaminated area or an area subject to contamination, consult with the manufacturer regarding permeation of pipe walls, jointing materials, etc., before selecting materials for use in that area."