The hole size 4" and overall height 17 3/8" is the same. The only difference is the overall diameter of the cartridge... the C800 is 8.5"...the C900 is 8 15/16"..this means I would have less than 1/4" (3.5/16th")difference on each side. Will this cause a problem ?
Since the height and hole size are the same, the cartridge should fit well except for that weee bit of space left to right (overall diameter). I even notice that the current proper cartridge for the c800 does not fit snug to the sides.
I am replacing the c800 due to some small vertical cracks on the housing (not the top) where the lid snugs down. The new O ring gasket no longer prevents water from flowing from underneath the lid. I have put some marine epoxy on the cracks today but I think that will only be a short term solution.
Any help would be much appreciated. I have 3 perfectly good C800 filter elements that I don't want to throw away.