Nobody drains a pool for fun. It’s a day of logistics, a water bill you can feel, and an empty concrete hole where the backyard’s best feature used to be. So the question comes up constantly: do we really have to?
In Arizona: yes, on a cycle most of the country doesn’t need. The typical East Valley pool wants a drain-and-refill roughly every three to five years — and the reason is in the tap water.
The problem evaporation can’t solve
An East Valley pool loses enormous water to evaporation — inches per week at summer peak, several feet over a year. Here’s the part that drives everything: only the water evaporates. Every mineral, salt, and chemical byproduct stays behind in the remaining water.
Then you top off with tap water that’s already among the hardest in the country, adding a fresh load of calcium and dissolved solids. Evaporate, concentrate, refill, add more. Repeat weekly for years. Your pool is a giant reduction pot, slowly stockpiling three things:
Calcium hardness. It climbs and climbs until the water physically can’t hold it, and it starts depositing as scale — the white tile-line crust, rough plaster patches, and the invisible coating inside your heater and salt cell. Chemistry can manage high calcium; nothing but dilution can remove it.
Cyanuric acid (stabilizer). Every chlorine tab adds a little. Stabilizer is necessary armor against our UV, but past a threshold it over-shields chlorine to the point of uselessness — pools with sky-high CYA show “good” chlorine readings while algae grows anyway. It leaves the water only one way: down the drain.
Total dissolved solids (TDS). The grand total of everything dissolved in the water. High TDS makes every chemical you add work worse — you dose more, get less, and the water never quite feels or looks right.
Old water is expensive water. The pool starts consuming chemicals faster while responding slower, and no amount of product fixes it, because product isn’t the problem — the water itself is used up.
Signs your pool is due
- Chlorine demand keeps rising even though nothing else changed
- Persistent cloudiness that survives correct chemistry and a clean filter
- Scale spreading at the tile line and on the plaster
- Stabilizer reading far above target on every test
- Algae pressure despite chlorine readings that “look fine”
- Salt cells, heaters, or filters needing attention noticeably more often
Any two of those together, and a test for CYA and TDS will usually settle the question.
When to drain — and when not to
The calendar matters more here than anywhere. Drain in the cool months, roughly October through April. An empty pool in an Arizona summer is a genuine hazard to itself: exposed plaster dries, shrinks, and cracks fast in 110-degree sun, and even the shell’s structure can suffer. Add peak-season water costs for the refill and summer draining is a lose-lose — done only when a swamp-condition rescue truly forces it, and managed on a tight clock when it is.
The other timing note: a drain is the natural moment for surface work. If your plaster is stained or scaled, an acid or chlorine wash while the pool is already empty costs far less than a separate drain later just to do the same job.
Stretching the interval
You can’t beat evaporation math, but you can slow it down. Consistent chemistry keeps calcium managed instead of depositing early. Switching from heavy tab use toward a salt system stops the stabilizer creep entirely. A pool cover slashes evaporation itself in the off-season. And weekly monitoring means the drain happens when the numbers say so — not two years after the water quietly went bad.
That monitoring is baked into weekly service: we watch the trend lines, tell you when a drain is approaching, and schedule it for the right season instead of the desperate one. If your water hasn’t been changed in memory and the pool is acting like it, ask us to test it — the numbers will tell us both what’s true.