The answer depends on what your bathtub is made out of, as bleach can damage some tubs. Tubs containing iron should never be cleaned using bleach because it can cause the iron to oxidize, leaving red streaks that can stain permanently. Also, acrylic and enamel bathtubs should not be cleaned using bleach, although some manufacturers say that the use of powdered oxygen bleach is safe on some types of acrylic baths; check the manufacturer’s instructions for your bath type. Even where you can use bleach, always dilute it to avoid discoloration or staining the tub. For detail on cleaning a bathtub using bleach, see How to Clean a Bathtub with Bleach.