Posted: 19/09/2013 at 09:41
Have you considered boxwood shrubs?
A Green Velvet Boxwood grows about 4-6 feet upon maturity and also fast growing. Best for growing zones 5-8. Since the mature width is 3-5 feet, I don't think the roots can reach and damage the pipes. But i'm not sure though. It's just my guess. I never heard anyone having problems with pipes when it comes to shrubs.