Hi fellas
Just a quick little question that I have always wondered and perhaps someone knows the answer to regarding the RO system.
Why is it that the first filter has a clear housing and the other filters have ones that are not clear? The clear one always ends up having the green algae spread all over and I often wonder if there is a reason it is clear as if there isn't I'd change it to a different one.
Hope that's clear, thanks.
Tom 
Don's 100% correct with his answer.
However our r/o's clear housing has never been green with Algae, even when our r/o was in the sun next to the back tap. It was always a brown slimy sludge all over the filter which is sediment in the water. Chlorine is still in the water in the sediment prefilter so algea shouldn't grow as chlorine kills it.
When I put my 4040 together I opted for clear housings, but also fitted a pressure gauge on each side of the prefilters. Now I can see at a glance when the sediment prefilter needs changing by looking at the pressure gauges. When the difference is 10 psi then I change the sediment filter. (Our water can be very sediment laden, and have often changed the sediment filter three times to a single fiberdyne carbon block filter change.)
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