Our shower has a plastic, Target-brand clear shower liner and then a fabric, cotton curtain. The plastic liner constantly fills with mold and/or soap scum every 6 months. I've heard that you can throw these things in the washing machine, but I've never tried. Spraying cleaners, natural or otherwise, doesn't do much. The liners are only $6, but I feel guilty about having this consistently replaced. What are my alternatives?