Chance of Contamination Entering Well From a Water Storage Tank

[Rainman]

Is there an increased chance of contamination entering back into the well from a water storage tank that refills with a float set up rather then installing a back flow preventer? How difficult is it to check a back flow preventer once a year?

What is the potential of a 2,500 gallon buried white plastic water storage tank becoming contaminated with it's float set to refill the tank after 300 gallons have been drawn off knowing the total monthly water usage is only 1,000 gallons per month?

Thanks For Your Help it's Greatly Appreciated!!

[speedbump]

It would seem to me that any storage tank that is not under pressure and sealed up, will grow bacteria. It may or may not be harmful, but it can become rather stinkie after a while. A little chlorine added to the tank occasionally is an easy way to keep it disinfected. You can drop some in manually or have a Feed Pump do it for you each time the pump runs to fill the tank.