Depends on your area, a friend works at local refinery. In our area we have inspections on fuel storage facilities every so often. The inspectors claim the popular stations don't change filters and clean out tanks like they should because they are to busy and don't want to be offline for a period of time. I am lucky as we have a farm co-op fueling station for the many farmers in the area. They go overboard in the fuel maintenance and always pass inspections with flying colors. Some areas have no required inspections and those areas are the ones to stay away from. The big city near us, just busted a number of popular stations for excess water and other crud in their tanks. I never buy gas in the city, have had to many issues in past years. We have a number of trailered boats coming out into our country co-op to fuel their boats. Best bet is to check your fuel frequently for impurities and water.High volume gasoline stations have the least water in their tanks. They have thought of raining when filling. Stick with them for clean fresh fuel.
Do install a water separator, however.