Pausing the contract for summer travel
Owners leave for July and August and suspend maintenance to save a month's fee, then return to a green pool that costs more to recover than the paused visits would have. Heat, evaporation and shamal dust make summer exactly the wrong season for a pool to be unattended.
Judging the pool only by clarity
Sparkling water can still be over-stabilised, under-sanitised or corrosively unbalanced. Clarity lags chemistry by days. Insist on seeing actual readings for free chlorine, pH and, in summer, cyanuric acid, rather than accepting a visual all-clear.
Buying a heater or chiller on price alone
An undersized heat pump runs continuously, inflates the electricity bill and still misses the target temperature. Size the unit to your pool volume and desired season, and have the coil cleaned before each winter, because a summer of dust halves its efficiency.