What a Drain and Refill Actually Corrects
Pool water is not simply reused season after season without consequence. Every chemical treatment — chlorine, pH adjusters, algaecides, stabilizer — leaves behind dissolved residue. While filtration removes suspended particles, it cannot remove dissolved compounds. Over time, the water's total dissolved solids (TDS) level rises beyond what standard chemistry can counteract.
A drain and refill is not a maintenance shortcut. It is the appropriate response when water has reached a saturation point that makes further balancing ineffective. Common indicators that a full replacement is warranted include TDS readings consistently above 1,500–2,000 ppm above the fill water baseline, cyanuric acid above 80–100 ppm, calcium hardness above 400 ppm causing persistent scale, recurring cloudiness that does not resolve after repeated chemical correction, combined chlorine that returns within days of shock treatment, and post-contamination events where complete water replacement is the safest reset. Attempting to manage severely degraded water through chemical additions alone increases costs, stresses equipment, and often produces unstable results.