erratic air tank

The air pressure tank started acting erratically two days ago, causing surges that result in water leaks and toilet fill valves not shutting, causing the toilet to run constantly. This happened overnight, which emptied the well and when I turned on the faucet ,sediment from the bottom of the well poured out.The air tank is 20+yrs.old. Do I need a new one ? It is a WellXtrol by Amtrol.. How hard is it to replace?

If "acting erratically" means clicking off and off very fast, then yes your tank maybe bad. See the sticky above about maintenance of a bladder tank.

The leaks and running toilet valve are caused by the debris that has been pushed into your supply piping. Replacing a 20 year old tank might be a good starting point, but it would be best to confirm that the rest of the system is operating properly with no air/water leaks in the well or supply to the house.

Surging and turbidity may be the result of air getting into the system, possibly from sucking the well dry.