i have heard that the salts in tap water will do that if can collect rain water or if out in country look for small stream or spring or river because they are fed by springs, rain or melting snow or ice just check water ppm before useing it to make sure if plants and fish live in it ilbe safe to use but dont have nothing close by i know wall mart carrys a flter and pither that claims to take the ppms to 0 and also comes with a ppm meter