Everyday in the summer, when I was growing up, my mom would drop my brother and I off at our grandmothers before she headed off to work. We loved spending summer days at grandma’s house – she had the best snacks, would take us to the movies and she had a pool in her backyard.
So every morning, we would join her in “pool duties.” One of us would use the net while the other one would use the brush to clean the pool. Grandma was always in charge of testing the water and adjusting the chemicals as needed.
She always emphasized that if you wanted to enjoy the pool, you had to take care of it. I guess that’s a lesson that applies to more than just pools. Here’s a few tips I learned from her.
The Turn
Here’s something most pool owners don’t realize until something goes wrong: a pool can look perfectly clear and still be completely out of balance. Beautifully blue water is not the same as safe, properly balanced water. Chemistry doesn’t care about appearances. And if you’ve ever left testing up to your pool store, it’s worth asking a question nobody really talks about — whose interests are they testing for?
Why Balanced Water is Non-negotiable
Pool water chemistry isn’t just about keeping things pretty, though that’s a nice side effect. When the water falls out of balance, the consequences range from mildly annoying to genuinely expensive.
For the people in it
Water that’s too acidic or too high in chlorine irritates eyes, dries out skin, and can bleach swimsuits after a single dip. Improperly balanced water also allows harmful bacteria and algae to thrive — chlorine loses most of its sanitizing power when the pH is off, even if the chlorine level itself looks fine on a test strip. That means you can have plenty of chlorine in the water and still have a pool that isn’t actually sanitary.
For the pool itself
This is where things get expensive. Water that’s too acidic — low pH, low alkalinity — will slowly eat away at your pool’s surfaces. Plaster pits. Grout dissolves. And yes, tiles can literally fall off the wall. Acidic water also corrodes metal components: pump parts, heater elements, ladder hardware. On the flip side, water that’s too alkaline or too high in calcium causes scale buildup — that white crusty ring around the waterline, or rough deposits inside the pipes and on equipment. Scale is hard to remove and costs money in scrubbing, acid washing, or early equipment replacement.
For your equipment
Your pump, filter, and heater are expensive. Balanced water extends their life. Out-of-balance water shortens it. It’s that simple.
What Your Actually Testing – and What the Numbers Mean
Pool chemistry sounds intimidating until you realize it’s really just six numbers, each with a target range. Here’s what they are and why each one matters:
pH — Target: 7.2–7.6
This is the most important number in your pool. pH measures how acidic or basic the water is on a scale of 0–14. Below 7.2 and the water is acidic — uncomfortable for swimmers and corrosive to surfaces. Above 7.6 and chlorine becomes significantly less effective, algae gets comfortable, and scale starts forming. pH drifts constantly. Test it at least twice a week.
Total Alkalinity — Target: 80–120 ppm
Think of alkalinity as the buffer that keeps pH from swinging wildly. Low alkalinity lets pH bounce all over the place — sometimes called “pH bounce.” High alkalinity makes pH sluggish and hard to adjust. Get alkalinity right first; pH will be easier to manage once it is.
Free Chlorine — Target: 1–3 ppm
Chlorine is the primary sanitizer. Too little and bacteria, algae, and other pathogens can take hold. Too much and it irritates swimmers and can bleach surfaces. One thing most pool owners don’t know: chlorine is much less effective at a high pH. At pH 8.0, only about 3% of your chlorine is doing any actual sanitizing work. At pH 7.2, you’re getting close to 60%. This is why pH and chlorine are always read together — one without the other is only half the picture.
Cyanuric Acid / Stabilizer — Target: 30–50 ppm
If your pool is outdoors and you use stabilized chlorine tablets (which most people do), cyanuric acid builds up over time. It protects chlorine from being broken down by UV sunlight, which is great — but too much of it and the chlorine becomes less effective even when levels look normal. This is sometimes called “chlorine lock.” The only real fix for high cyanuric acid is a partial drain and refill. Many pool owners don’t test for this at all, and many pool stores conveniently forget to mention it.
Calcium Hardness — Target: 200–400 ppm
This one matters most for plaster, gunite, and pebble pools. Water that’s too low in calcium will pull it right out of your pool’s surfaces — literally dissolving the plaster. Water too high in calcium leaves white scale deposits everywhere. Fiberglass and vinyl pools are less affected, but calcium still plays a role in overall water balance.
Total Dissolved Solids (TDS) — Under 1,500–2,000 ppm above fill water
Over time, as chemicals are added and water evaporates, dissolved solids accumulate. High TDS makes the water feel “heavy” and makes it harder for chemicals to work effectively. The fix is a partial or full drain and refill. This number tends to climb gradually, which is why most pools benefit from a partial drain every few years.
How To Test Your Water – Your Options
Test strips are the easiest starting point and the most widely used. Dip a strip, wait 15–60 seconds, and compare the color blocks to the chart on the bottle. They’re affordable (a bottle of 50 runs $10–15), portable, and good enough for weekly monitoring. The downside: they’re less precise than other methods, especially for readings at the edges of normal ranges, and the color comparisons can be tricky in bright sunlight.
Liquid drop-test kits (the kind that come in a case with reagents and test tubes) are more accurate than strips. The Taylor Technologies K-2006 kit is the one most pool professionals actually use at home — it tests all the essentials with better precision. They take a few more minutes but the readings are more reliable.
Digital test meters (like a digital pH pen or a photometer kit) are the most precise option for home use and have come down in price significantly. They eliminate the color-comparison guesswork entirely. If you find yourself fussing over readings, a digital meter is worth the investment.
Pool store testing involves bringing in a water sample for a computerized analysis. More on that below.
A few testing tips worth keeping in mind: collect your sample elbow-deep, not from the surface (where chemicals and sunlight concentrate). Test in the morning or evening, not in the heat of midday. And test consistently — same time of day, same spot in the pool.
The Pool Store Question: Are They Testing You or Testing Your Water?
Let’s be honest about what’s happening when you take a water sample to a pool store.
Pool stores do use computerized water analysis systems — the most common is the AccuBlue system, which tests multiple parameters quickly. These machines are reasonably accurate. The data isn’t fake. But data and recommendations are two different things, and this is where consumer awareness matters.
Pool stores are retail businesses. Their primary goal is to sell chemicals. The staff at the counter are often incentivized — directly or indirectly — to move product. And multiple independent reports, consumer investigations, and pool forums have documented a consistent pattern: pool stores frequently recommend more chemicals than are actually necessary, sometimes dramatically so. A pool that needs $20 worth of adjustment may leave the store with a $150 bag of products.
There’s a particular tendency to oversell calcium hardness adjusters, phosphate removers, and pool clarifiers — products that are often unnecessary or can be addressed with simpler (cheaper) means. Phosphate removers, for instance, are a topic of real debate among pool professionals: many argue that if your chlorine levels are properly maintained, phosphates simply don’t matter enough to treat separately.
This doesn’t mean every pool store employee is trying to deceive you. Many are genuinely trying to help, and some are quite knowledgeable. But the incentive structure creates a conflict of interest worth understanding. When the business model depends on selling chemicals, the recommendations will tend to favor chemicals.
What to do instead:
Test your own water at home first, before you ever walk into a store. Use a reliable liquid test kit or digital meter. Know your numbers before anyone else tells you what they are. Then, if you bring a sample in, you can compare — and you’ll be in a much better position to evaluate whether the recommendations make sense.
Cross-reference with a second source if anything seems off. Pool math calculators (PoolMath by TroubleFreePool is the one most pool enthusiasts trust) let you enter your exact readings and calculate precisely how much of any chemical you need to reach your target. It’s free, it’s math, and it has no interest in selling you anything.
It’s also worth knowing that some pool stores offer more trustworthy service than others. Independently owned pool supply shops often have staff with deeper technical knowledge and less pressure to upsell. And some Leslie’s locations genuinely do give good advice — it varies by store and by employee. The point isn’t to distrust every number they give you; it’s to walk in informed rather than relying entirely on their recommendations.
A Note for Those Who Inherited a Pool
If you bought a house with a pool and are new to this, know that the learning curve is steeper than it looks — but not unmanageable. The first season is mostly about understanding your specific pool’s baseline: how fast it loses chlorine, how pH tends to drift, what its calcium hardness looks like given your local fill water. Once you know those patterns, maintenance becomes routine. Start with a good test kit, take your own readings weekly, and treat the pool store as one input among several rather than the final word.
Finally
As much as I learned from my grandmother about pool care, to be honest I still choose to have a pool maintenance company service my pool once a week. The scheduled maintenance is on Mondays, but I still check the chemistry on Fridays to make sure I am getting my money’s worth. I always believe in being an informed consumer.
And, when a monsoon storm rolls through I clean out the all the debris as soon as possible. Leaving all that mess in the pool for someone else to clean won’t help the health of your pool.
I wish you a healthy pool that you really enjoy!