Deciding when your pool needs acid washing depends on a few key factors. If you’re dealing with tough stains that don’t respond to regular cleaning methods like scrubbing or chemical treatments, it might be time for an acid wash. Mineral deposits can build up over time, leading to discoloration and rough spots on the pool’s surface. Pools that have been neglected or exposed to hard water for long periods can also benefit from periodic acid washing to preserve their appearance and structural integrity.