Musty towels are a buildup problem, not a detergent problem.

The reset wash:

  1. Wash in the hottest water safe for the fabric.
  2. Add 1 cup of white vinegar instead of detergent. This strips buildup.
  3. Run a second cycle with half the normal detergent. No fabric softener.
  4. Dry completely before folding.

Ongoing habits: hang immediately after use, wash after 3 uses maximum in summer, and skip fabric softener – it reduces absorbency over time.