I recently developed a new water feature in my back garden. A nice little pond which formed each time I emptied the bath. I have had Dyna-rod over who kindly inspected the pipe with a camera and have told me that there is a lump of concrete in the pipe which is causing the problem, but that the pipe is undamaged / OK. Currently the water feature has subsided and there hasn't been any recurrence, but Dyna-rod have suggested that we need to dig up the pipe, cut out the section containing the concrete and then fix the cut pipe. They're not actually offering to help with any of this. What I don't understand is if there isn't actually a brake in the pipe, how is water escaping (is there an overflow?). How did a big lump of concrete get in the pipe in the first place when I've got grates on all the drains? Is there anything else I could do which doesn't involve digging the garden up (i.e. dissolving the concrete)? I know nothing about plumbing and would really appreciate any advice. Thanks