Jm's have basically shallow root systems...but I have found with age this is sort of of old cogers tale... with age they can become pretty deep . I personally DON'T think it will cause problems to the pipe cause the type of roots JM's have are not the type to do so no matrter how deep they go that being said.... I also don't think it's a good iea ...Many Jm's even in our area can get big and if you ever have to dig up the pipe or do some doctoring to it you will be forced to move the tree and be forced to do it in possbly the WRONG time when it will be suseptable to stress disease and kaputting!!!! So I would agree with your Hubbie although for the opposite resons...it's what a damaged pipe can do to the tree NOT vis a versa... David