Originally Posted by UCSF2012
Chemical cleaning isn't as effective as mechanical. In other words, use a brush.
...or you can just put in new pipes. PVC pipes don't corrode.
You are right in a sense - it really does need to be a combination of chemical and mechanical cleaning. This morning I was so distraught over the then-defunct fountain that I took the whole thing apart. The filters around the engine were clogged with dirt and debris, as it turned out. I submerged everything (except the electrical in/out ports) into a running soapy bathtub and voila - working like a charm now.