I have just $50 to buy a water filter. I have 50 gallons in garage of drinking water and 40 in the RV. I have another 50 gal for cleaning and flushing the toilet. I live 7 miles and a thousand feet above the river which is nearest water source. The water treatment plant is that far also so I am not worried about flushing.7 miles of down hill pipe. What would be my best bet for cleaning the river water? I have plenty of bleach and shock on hand. I can't afford a Berky at this time and feel like I better do something now. What is my best bet with $50?