Drain and refill is the only real solution for hard pool water.

Yes, but don’t drain it all at once. Water hardness comes from dissolved solids (mostly calcium and magnesium), and no chemical treatment truly removes them. The only way to lower hardness is to dilute what’s in there with fresh, softer water.

Here’s the safe method: drain about 25-30% of the pool, then refill. Wait a day for everything to mix, test the hardness, and repeat if needed. Draining more than that risks floating your pool (if the water table is high) or damaging the plaster/liner from exposure. For vinyl or fiberglass, never drain more than halfway unless the manufacturer says it’s okay.

Check your local ordinances before draining. Many areas require you to discharge into the sewer or a dry well, not the street or storm drain. And always turn off the pump before the water level drops below the skimmer—running dry destroys it fast.

Test after each refill. You’ll know you’re done when hardness drops below 400 ppm (ideal is 200-300). The process takes patience, but it’s cheaper than replacing equipment corroded by scale.