June to September: when chlorine cannot keep up
Evaporation is the other silent load. Losing five millimetres or more a day does not just lower the waterline; it concentrates everything left behind, so calcium hardness and total dissolved solids climb steadily through the season. That is why summer top-ups matter and why an autumn partial drain-and-refill is normal practice here, not a sign of neglect.
Frequency has to rise with the temperature. A pool that was fine on one visit a week in February generally needs two in August, with the technician brushing walls, emptying baskets, backwashing more often and adjusting dosing at each visit. Pump run times should stretch too: eight to ten hours a day in high summer is typical, against four to six in winter.