I have a problem with rust (I think) and other stuff clogging the screen (or is it a filter?) of my KWC shower mixing valves. See attached pictures. For the past 6 years since I installed the valves, I have had to clean them out every 3 months or so because hardly any water came out the shower head. And as of this summer, I have to clean them every 4 weeks. The picture shows one screen the way it looks after just 4 weeks, the other one is clean after I remove the gunk with a tooth brush.
My question(s): What is that stuff that collects in the screens? The brown stuff is almost slimy. I assume it's rust, but where would it come from? My house is connected to city water. Most of the pipes are copper, except for one bathroom that is unused. Landscape pipes are partially old rusted galvanized, but there is a backflow preventer that stops rusty water from flowing into the house. What is the white and the green chunky stuff? the white stuff feels greasy.
Any ideas? I'm getting tired of disassembling the valves and clean them out so frequently...