Pool chemistry intimidates a lot of new owners, but the actual numbers you need to remember are short. Six values, tested once or twice a week, will keep your water clear, your equipment safe, and your skin and eyes happy. Get the levels right and most of the “mystery” problems pool owners hit — cloudy water, eye irritation, scale on the tile line, short-lived chlorine — simply go away.
Here’s the cheat sheet, then a breakdown of what each one actually controls and what happens when it drifts.
Ideal pool chemical levels at a glance
| Parameter | Ideal range | Test frequency |
|---|---|---|
| Free chlorine | 1.0 – 3.0 ppm | 2–3x per week |
| pH | 7.4 – 7.6 | 2–3x per week |
| Total alkalinity | 80 – 120 ppm | Weekly |
| Calcium hardness | 200 – 400 ppm | Monthly |
| Cyanuric acid (stabilizer) | 30 – 50 ppm (outdoor) | Monthly |
| Salt (salt pools only) | 2700 – 3400 ppm | Monthly |
Free chlorine: 1.0 – 3.0 ppm
Free chlorine is the sanitizer doing the work right now. It kills bacteria, oxidizes organic gunk, and keeps the water clear. Below 1.0 ppm and you risk algae and bacteria. Above 5.0 ppm and you’ll smell it, your eyes will burn, and your liner and o-rings will degrade faster.
If your chlorine reading is zero but you know you added chlorine recently, you likely have combined chlorine — sanitizer that’s already been used up fighting contaminants. The fix is a shock dose with a calcium hypochlorite granular shock to break the chloramines and reset the system.
pH: 7.4 – 7.6
pH is the master variable. At a pH of 7.5, chlorine is about 50–60% effective. At pH 8.0, it drops to under 30%. This is why your pool can read “3 ppm chlorine” on a strip and still look cloudy: the chlorine is there, it just can’t do its job.
To lower pH, use a dry acid (sodium bisulfate) pH Down reducer — safer to handle and store than liquid muriatic acid for residential users. To raise pH, use a soda-ash-based pH Up increaser. Add chemicals slowly with the pump running, then retest after the pool has circulated for at least an hour.
Total alkalinity: 80 – 120 ppm
Total alkalinity is the buffer that keeps pH from bouncing around. Low alkalinity makes pH swing wildly, which crashes chlorine performance and can etch plaster. High alkalinity locks pH in a high state and causes scale. Fix alkalinity before you chase pH — if alkalinity is right, pH usually settles into range on its own. To bring a low alkalinity reading up, dose with a sodium-bicarbonate-based total alkalinity increaser per the label rate for your pool volume.
Calcium hardness: 200 – 400 ppm
Calcium hardness controls scale and corrosion. Too low (below 150 ppm) and the water becomes aggressive, etching plaster and corroding metal. Too high (above 500 ppm) and you’ll see white scale on your tile line, salt cell plates, and heater elements. Vinyl liner pools tolerate slightly lower numbers, but stay above 150 ppm to avoid foaming and equipment wear.
Cyanuric acid: 30 – 50 ppm
Cyanuric acid (also sold as “stabilizer” or “conditioner”) protects free chlorine from being blown apart by UV. Without it, outdoor chlorine breaks down in a few hours of sunlight. With too much (above 80 ppm), chlorine becomes sluggish and your pool needs higher and higher doses to stay sanitary. Indoor pools don’t need stabilizer at all. If your reading is below 30 ppm, add a granular chlorine stabilizer gradually through the skimmer over several days and retest before adding more.
Salt: 2700 – 3400 ppm (salt pools only)
If you run a salt chlorine generator, salt is what your cell converts into chlorine. Most cells target 3200 ppm and will start throwing “low salt” warnings below 2700. Don’t guess based on the salt cell’s own readout — sensors drift. Use a separate salt strip or kit once a month.
The test kit decision
Test strips are convenient but inaccurate, especially for chlorine and pH at the edges of the range. A liquid drop kit is the right tool for any pool owner who’s serious about getting numbers they can actually act on. The Taylor K-2005 and K-2006 are the gold standard residential kits, and the salt version covers everything plus salt for a saltwater pool.
Taylor K-2006 Complete Test Kit (FAS-DPD)
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Taylor K-2005 Complete High DPD Kit
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Taylor K-2005 Salt Pool Test Kit
Shop NowThe Durachlor chemicals to keep on hand
The chemistry above is only useful if you have the right chemicals at the pad when a reading drifts. Durachlor covers every adjustment a residential pool needs — shock, pH up, pH down, alkalinity, and stabilizer — in resealable buckets sized for a typical pool. All five are in stock and shipping from our warehouse, currently at roughly half off compared to MAP:
Durachlor 1 Lb Assault 73 Granular Shock
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Durachlor 5 Lb pH Down Reducer
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Durachlor 5 Lb pH Up Increaser
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Durachlor 5 Lb Total Alkalinity Increaser
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Durachlor 2 Lb Chlorine Stabilizer
Shop NowWhen and how often to test
For a residential pool in active use, test free chlorine and pH two to three times a week, alkalinity weekly, and the other parameters monthly. Test after heavy rain, after a pool party, and after any chemical addition. The goal isn’t perfection on every reading — it’s spotting drift early so a small adjustment fixes what would otherwise become a green-pool weekend.
If you’re not sure where to start
Reach out to PST Pool Supplies and we’ll help match a test kit and starter chemistry pack to your pool’s size, surface, and sanitizer system. Better numbers means less chemical use, longer equipment life, and a pool you actually want to swim in.