I have a mildew odor problem. We have a shower enclosure (fiberglass I thnk). There is a very strong smell of mildew I believe coming from the overflow drain in the tub. I have attached a picture of where I think the odor is coming from. We are only at this house a few days a week so the water is not used for several days. Even after we run the shower it still smells. Any ideas would be greatly appreciated.
Start with some bleach and clean up around the tub lever and drain. You can remove those screws and spray some mildew remover in there to help out. Just don't use ammonia products with bleach products, and it should go away.