Water Chemistry

Pool Chemical Balancing Explained

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Pool chemistry sounds complicated because the numbers are interdependent, not because any single reading is hard to understand. Unincorporated Harris and Montgomery County lots around Tomball and Magnolia often run on septic and private well systems, so equipment pads, plumbing runs, and excavation are planned around those systems during the site evaluation, not discovered mid-dig.

Twilight indoor infinity pool with glass wall reflections

The Four Numbers That Matter

Free chlorine (or bromine) is the sanitizer killing bacteria and algae; pH measures how acidic or basic the water is; total alkalinity is a buffer that keeps pH from swinging; and calcium hardness measures dissolved minerals that affect plaster and equipment.

Of the four, pH and alkalinity move together. Alkalinity below about 80 ppm lets pH bounce around with every rain event or chemical addition; alkalinity above about 120 ppm makes pH stubborn and hard to correct. Fix alkalinity first, then dial in pH.

A Practical Order of Operations

Test alkalinity and pH before adding sanitizer. If alkalinity is out of the 80-120 ppm range, correct it with the appropriate increaser or decreaser and retest the next day before touching pH.

Once alkalinity is stable, adjust pH into the 7.2-7.6 range. Only then does chlorine work as efficiently as it should; chlorine added to water with the wrong pH is partially wasted, which is a common reason a pool "won't hold chlorine" even with frequent dosing.

FAQs

How often should I test pool water?

Twice a week is a reasonable baseline for most residential pools in the Houston area given the long swim season, more often during heavy use (parties, frequent rain) or right after shocking.

Why does my chlorine reading keep dropping overnight?

UV exposure burns off unstabilized chlorine, and heat accelerates the process; a cyanuric acid (stabilizer) level in the 30-50 ppm range protects chlorine from sun loss without over-stabilizing the water.