How often should you test your pool chemistry?

Why bother

Off-balance water turns green or eats the liner. A thorough-tier job. Skippable when life's busy, worth it when it isn't.

What the job involves

1. Scoop a sample from elbow-deep, well away from the return jets and the skimmer, so you read the bulk of the pool and not a fresh-chemical pocket sitting by the inlet.
2. Test free chlorine and pH first, since those two move every day. Dip a strip for one second and read it against the chart, or use a liquid drop kit if you want it precise. The CDC wants pH between 7.2 and 7.8 and free chlorine at 1 ppm, or 2 ppm if you run a stabilizer.
3. Check total alkalinity at least weekly, and calcium hardness and cyanuric acid now and again. Alkalinity is the buffer that stops pH bouncing around, so it does a lot of the quiet work.
4. Adjust what's off: chlorine, a pH increaser or decreaser, an alkalinity adjuster. Then let the water circulate a few hours and test again before you call it sorted.

Do it yourself, or pay someone?

Yourself, easily. Strips run about $15 to $40 a year, a decent liquid kit is a one-time $30 to $70 and lasts seasons, and the skill is dip, compare, adjust. A weekly pool service that includes testing runs roughly $80 to $150 a month (Angi), worth it only if you'd rather not touch the water at all. Most pool-supply stores will test a sample for free if you want to check your home kit against theirs.

What skipping it costs

$450 to $15,000, but only once skipped testing has let the water go off long enough to do damage, and that's the catch: balanced water costs a strip and a minute, while unbalanced water quietly eats the pool. The cheap end is an acid wash or a drain-and-clean of a green pool, around $450 to $1,500. The middle is corrosion from acidic water working on the metal: a heater repair averages about $479, or a replacement at $1,600 to $5,200. The far end is resurfacing a pool the chemistry has etched and pitted, $6,000 to $15,000. None of that corrosion comes back once it's done, it only gets repaired, and chemistry damage voids most heater warranties on top.

Signs it's overdue

• Cloudy, hazy, or faintly green water, or a strong chemical reek off the surface. That 'chlorine' smell is chloramines from too little free chlorine, not too much, so it means the opposite of what you'd think.
• Stinging eyes, itchy skin, or swimsuits going faded after a swim, the usual tell that pH has drifted out of the 7.2 to 7.8 range.
• White crusty scale creeping along the waterline, tiles, and ladders, or rust on the metal rails and equipment. That's calcium or pH having been off for a good while.

When to start thinking about it

No notice needed, really. Grumpty mentions it the day it comes due and that's that. Mark it done and Grumpty sets the next one, every week, so you can go back to forgetting it exists.

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