I have an air leak at the top where the pressure gauge is, causing the filter housing to be about 1/2 full of air in the morning. It that a replaceable part or do I have to buy the entire top half of the filter housing? It's starting to look rather old and weathered so was wondering how long they last anyway. Maybe I should just buy an entire fiberglass filter housing and get rid of the old one? It's close to 7 years old.