There are 2 simple ways to keep your water tank clean. Step 1 Always use a food grade rated water hose to fill your tank and always check the water pipes before the tap. Both garden hoses and the wrong type of poly pipe can give your water a disgusting plastic taste. And once you get this toxic mixture in your tank, it’s difficult to get rid of. I wrote about this in detail – see the section on “Be Careful Where You Fill Up…”. If you follow these guidelines, you’ll never have to worry about a tankful of foul-tasting water. Step 2 Always sanitise your water tank after each fill. The best product by far is BioMagic WaterPure. It’s completely taste-free, odourless and is a biological solution, rather than being full of nasty chemicals. We’ve been using BioMagic for over 4 years, with no issues at all. It keeps our tanks clean and prevents any algae or pathogen growth in your water tank. Related Questions - How to fill an RV water tank with fresh water. - Where to fill an RV water tank on the road. - Where to refill an RV water tank.