Establishing fresh potable water takes a chain of proper procedure and maintenance. You have to start with a good source, bad in=bad out. Be sure you're using a good RV or marine hose that will not add a taste to your water; a garden hose, for example, would make your water taste like rubber, whatever that tastes like. I don't believe the hose is a good place to save money, get yourself a top notch, quality, hose! From there I would install a set of filters, sediment and charcoal stages are what I use. Before you fill your on-board water tank, always use a sterilization process. Some use a bleach solution (I think because it's readily available...and cheap), I use a commercial product that doesn't leave the residual odor of bleach. Fill you tank with whatever solution you decide on and let stand for the recommended period, typically 24 hours. Drain the water tank and you're ready to refill with fresh, filtered, water.
While we're talking tank maintenance, you will avoid smells from your grey and black water tanks by using similar maintenance techniques. Now this is where I do use bleach to try and kill bacteria in the waste tanks. We also pour a 50/50 mix of water and white vinegar to pour down the drain traps on a regular basis.
It will also help if you drain your water heater when you don't plan to use your rig for an extend period of time.