I seem to clean the Waterco pre-filter about 3-4 times per year. Algae grows on the sides of the clear bottom and some sludge seems to stick to it. So I unscrew the treaded clamp that holds the top and bottom together. This usually takes a little persuasion with a rubber hammer to get it started. Then I tap gently on the clear plastic at the joint of the two halves while lifting up at the same time, until it comes apart. I then hose out as much as gunk as I can then scrub out any remaining algae on the sides.
Prefilter before cleaning:
Over the winter I had a few freezing days and the plastic valve that lets you drain the prefilter must have expanded with ice. It now leaks a little when the valve is open. I need to replace that.
