Draining the tank should be done fairly often, several times a year, especially when used during months of high humidity. Water separators must be located quite far away from the compressor to be most efficient. Heated air from the compressor will hold a lot of water and be hard to separate. Cooler air makes the separator more efficient. I always used at least a two step separation when I was in business. First was a common filter/separator, commonly found at Harbor Freight. Then I used a desiccate filter and also a "toilet paper" filter. That was a common name for a filter that had a roll of brown paper in it. The desiccate and paper filter captured really fine water particles. Check with an automotive paint supplier if you want to shop local.