O-Rings are difficult to size
"These were the wrong O-Rings, way too big. I had some old 2. 5" external filter housings from 2013 and the O-Rings have changed slightly since then. The new filter housing O-Rings that look identical are actually a tiny bit thicker and larger diameter (see photo). The problem was microcracks in the top, which new O-Rings will not fix. I bought a new 2. 5" housing with top from US Watersystems and new 2. 5" O-Rings and the leaks stopped. The new O-Rings look like they will probably fit the new housing, if ever needed."



