One of the two I bought was missing an o-ring which made it quite a mess before I found out. After buying an o-ring (Pentek 151121 OR-38 Buna-N o-ring for Slim Line housing) it now works perfectly. Others have mentioned the leak. The sealing ring is inserted into the slot in the pan (transparent part). If you have a leak, turn the pan upside down and shake it. The 4 inch o-ring should pop out.
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