Our units have quartz sleeves rather than standard glass and we also use uprated T5 quartz UV lamps as a result the UV output is very intense compared to our competition. This makes for a very hard life on the U.V bodies meaning that the bodies will very slowly degrade over time, even though they are made from a UV resistant plastic. This is the same for all U.V units ( commercial and retail quality ).

The working life for a U.V body is around 6-10 years depending on flow rate through the unit at which point they should be changed as a matter of course due to effects of U.V on the body over time , this cannot be avoided due to the nature of high output UV-C .

UV-C at this exposure rate will pretty much attack anything bar some glass or metals, even then U.V can etch the hardest of materials over time.

The black particulate is benign and should be rinsed from the unit at every lamp change and the unit put back into operation.