Fire Dept do extremely lot of preventive maintenance.
I had Racor separator on my VW diesel installed by PO.
The aging orings on it were major source of troubles and headaches.
I deleted the Racor and problems stop.
I drive diesels in CA for almost 30 years and yet have to see water in diesel.
In last decade all US gas stations had to switch to double-wall tanks that prevent moisture in them.
On Powerstrokes fuel filter should be replaced every 30k. I made over 90k on my F450 while towing heavy before clog filter gave me some hesitation. The filter on Powerstroke is on top of the engine, so 5 minutes job to replace and electric pump does priming.