I'm not doubting the possibility of water issues, however, I do know a lot about fabrics. Line drying in the sun will cause fading faster than anything. And, I'm not sure of the origin of the fabrics either. Lesser quality fabrics quite often are not yarn dyed so that could be a problem when fading is spotty. Also, the quality of the dying process could be a problem. Perhaps a combination of all of these and the water purifying methods are causing your fabrics to lose their luster much faster than normal.