Routine chemical balancing
Weekly service commonly includes testing and ordinary adjustments for sanitizer, pH and related water-balance needs. The exact chemicals depend on the pool and current readings.
When treatment becomes more involved
Green water, algae outbreaks, unusually high demand, contaminated water or a major imbalance can require more chemicals and labor than normal weekly maintenance.
Ask for clear terms
Your agreement should state whether standard maintenance chemicals are included and explain that recovery treatments or extreme conditions may be priced separately.