Bladderless tank - pressure issue

I had to replace / repair a sediment filter (in front of the bladder less pressure tank). To do this I shut power to the well pump, opened a basement faucet and waited until the water flow stopped. I then opened the flush valve on the sediment filter to release any extra pressure. That done, I replaced the sediment filter, closed the faucet valves and restored power. The pump started, air was being drawn in by the aerator, and pressure increased. The pressure switch disengaged at 80 pounds (normal for me). No more air was being drawn in. However, the pressure gauge continued a slow rise to 95 and then bottomed out at 100 (gauge max is 100). If I hadn't heard the relay trip and the aerator stop drawing air I would think that the pump was still engaged ... thoughts ?

First I'd drain the pressure again and replace the pressure gauge. Then check it again. The pressure shouldn't continue to rise after the pump cuts off.

I don't how or why the pressure guage continued to rise after the pump evidently stopped. It would be good to know how and where the guage and switch are plumbed in. Given that you describe a micronizer and precipitation tank, both the guage and switch would have to be after the micronizer and subject to the buildup of iron oxide. The pump could well have taken the system to 100 PSI but the switch (and guage) were slow to react.

I made the mistake of placing my switch and guage into the water stream and have had to replace the switch once already. I started to distrust the pressure guage so I placed a second guage at the top of the precipitation tank where it is only exposed to air, not water. I plan to replumb the switch to the top of the tank as well.

I put a ballvalve on the intake to the tank after the micronizer so that I don't have to drain the system to service the micronizer or the Banjo mesh filter before it. The way my Banjo filter is designed, it cannot be subjected to high volume reverse flow or else it may crush the fine mesh screen. Also, the micronizer cannot be allowed to be subjected to reverse flow either or it can clog up with the iron oxide that precipitates downstream of it, so I just need to open the ballvalve very slowly after servicing.

If one buys a US 25$ gauge and puts it on a mini ballvalve, or a snubber, it outlasts 15] 4$ chinese joke gauges. Who needs to see the pressure during the 99.9% of the time you are not there?