Question
I have a confer hedge growing within 1 metre of the side of my house and a sewage pipe is buried alongside the foundation, will the roots of the hedge cause problems in the future, it has been planted 4 years and is about 3 metres high with little or no maintainance done to it  

Answer
Fine roots will grow any time and any place where 揼ood?conditions exist. That means the right balance of water, nutrients and oxygen. (Yes, oxygen. Roots are living tissue and need oxygen to respire.)  In urban environments, one place where this balance is optimal is residential drain tiles.  
IF one of these should break, tree roots are great  
at exploiting this new environment, proliferating and blocking the pipe. In a recent article in City Trees, Journal of the Society of Municipal Arborists, Jeff Heintz, City Forester of Bismarck, N.D., discussed the mechanical and chemical methods of destroying those roots. The chemical control options include a copper sulfate formulation, products with the herbicide dichlobenil, or those that contain metam-sodium.

Copper sulfate is the method often used by homeowners to control roots in sewer lines.  
The fine roots absorb the copper and die, but don抰 translocate the copper to the top of the tree.  
The same root pruning technique is often used  
in the nursery trade ?copper lined containers ? 
to keep plant roots from growing outside of the pot and to avoid spiraling roots. Products containing dichlobenil can be purchased over-the-counter at many hardware stores, though a more concentrated version is used by professional plumbers, drain cleaners, and municipal maintenance departments. Metam-sodium is highly effective and also highly toxic. It is only available to professionals.

The key is if there is a break in the pipe then the roots could get into the pipe and clog the drain. If you are concerned go ahead and treat the pipe with copper sulfate. The then every three or so years do it again.