How to Test Your Pool Water (and Why Strips Lie to You)
Buy a FAS-DPD drop-titration kit (the Taylor K-2006 is the standard) and test your own water. Strips are imprecise and can't read chlorine at the levels a green pool needs; pool-store computers are a dice roll on CYA — the same water can read very differently from store to store. Test FC and pH twice a week in season, CYA/TA/CH monthly, and always before and during a SLAM.
You cannot fix a pool you can’t measure — and the two cheapest ways to measure (test strips, the free pool-store test) are exactly the two that hide the numbers that matter. This is the one place where spending a little up front saves you a season of frustration and a shelf of wasted chemicals.
Why strips and store tests fail you
Test strips are imprecise, fade with heat and age, and often read total chlorine (free + combined) — so a pool full of chloramines can look “chlorinated” while true free chlorine is near zero. They also top out well below the chlorine level a green pool needs, so they’re useless for the one job that matters most.
Pool-store computer tests look official, but on CYA they’re a dice roll — owners who split one water sample across two or three stores on the same day report CYA answers as much as 100 ppm apart. That’s not a bias you can correct for; it’s noise, on the exact number that sets your chlorine target. A wrong-low reading starves your chlorine (green pool, “fine” numbers); a wrong-high one has you dosing chlorine you don’t need. (More on that in is the pool store a scam.)
What a real kit measures
A drop-based FAS-DPD kit reads all five numbers that matter — and, crucially, reads free chlorine accurately even at SLAM levels, which is the whole reason to own one:
| Test | Strips | Pool store | FAS-DPD drop kit |
|---|---|---|---|
| Free chlorine (low) | rough | ok | precise (0.2–0.5 ppm) |
| Free chlorine (high, for a SLAM) | ✗ can’t | ✗ won’t | ✓ yes |
| Combined chlorine (chloramines) | ✗ | sometimes | ✓ yes |
| CYA (stabilizer) | rough | inconsistent | ✓ accurate + repeatable |
| pH / TA / CH | rough | ok | ✓ accurate |
The one kit worth owning
You buy it once and refill the reagents for years — cheaper over a season than the chemicals you’d waste guessing.
The Taylor K-2006 is the gold standard: FAS-DPD chlorine, plus pH, TA, CH, and CYA in one case. Buy it once and refill reagents for years. The TF-100 (sold direct at tftestkits.com) is the same FAS-DPD kit with more reagent per dollar if you’d rather buy direct.
On a tighter budget?
The Taylor K-1004 is a big step up from strips for the everyday numbers and great for spas — but it uses the older DPD block (less precise, and it can’t read chlorine high enough for a SLAM), and it skips CYA and calcium hardness. Since CYA is the number the whole FC/CYA chart hinges on, we’d still point most pool owners at the K-2006. Get the K-1004 only if budget is the deciding factor or you’re mainly testing a spa.
One shopping trap while you’re comparing: Taylor also sells a K-2005, which looks like the K-2006’s twin and tests all the same numbers — but its chlorine test is the DPD color-match block, not FAS-DPD drops, so it also can’t read the high chlorine a SLAM needs. Same brand, near-same box, one letter apart — and the 2006 is the one that works when your pool is actually in trouble.
Yes, we just spent this whole page telling you strips are the weak way to test — and that stays true for chlorine, pH, and CYA. Salt is the exception. Salinity only needs a coarse read (your chlorinator’s happy range is hundreds of ppm wide), and strips are the cheap second opinion on the salt reading your chlorinator claims before you dump bags of salt in on its say-so. Salt-pool owners: keep the drop kit for the five numbers, add these for the sixth.
“These test strips make checking the salt level in my pool quick and simple. The instructions were easy to follow, the color chart was clear, and I was able to get a reading in just a few seconds. They seem consistent from strip to strip and save a lot of time compared to more complicated testing methods.” — Chris, verified owner · Amazon
Want the premium version of that second opinion? The Taylor K-1766 is the drop-titration answer to the strips: silver-nitrate drops, 200 ppm per drop, refillable reagents, and the same virtue that makes the K-2006 the standard — the same water gives the same answer every time. Strips are honestly fine for salt’s coarse read; the K-1766 is for the owner who already counts drops and wants the whole panel to work that way. Over a few seasons of strip bottles, it can even come out ahead:
“Saves money compared to salt strips and more accurate too. Complements my Taylor test kit which I purchased before the salt option was available. The case is the same color and material, for what that’s worth!” — A Customer, verified owner · Amazon
How to test (the fast version)
- Free chlorine + pH — twice a week in season, daily when it’s hot or busy, several times a day during a SLAM.
- CYA — monthly, and any time the pool goes green while chlorine “looks fine.” It sets your whole FC target.
- Total alkalinity + calcium hardness — monthly, or when pH won’t hold still.
- Combined chlorine (CC) — whenever the water smells like chlorine or eyes sting; above 0.5 means it’s time to SLAM (see the chlorine smell myth).
Once you can read your own water, everything else on Pool School is just doing the math — and the chemical calculator does that for you — or log every test in the free Pool Tracker to watch your numbers trend over time. Testing well is the whole of the less-is-more approach: measure, dose once, stop.
Frequently asked
Are pool test strips accurate?
Not accurately enough to run a pool. Strips are imprecise, fade with age and heat, and often read total chlorine (free + combined) rather than free chlorine — so a pool full of chloramines can look chlorinated when true free chlorine is near zero. They also can't read chlorine at the high levels a green pool needs. Use them for a rough daily glance at most; make real decisions off a drop-based FAS-DPD kit.
What is a FAS-DPD test kit?
It's a drop-titration kit that measures free and combined chlorine precisely by counting drops until a color changes — accurate to 0.2 or 0.5 ppm, and it reads high chlorine levels that strips and the OTO block can't. The Taylor K-2006 is the standard example; it also tests pH, total alkalinity, calcium hardness, and CYA. It's the only kind of kit that can run a SLAM.
How often should I test my pool water?
In swim season, test free chlorine and pH about twice a week (daily if it's hot, heavily used, or you're fighting something). Check CYA, total alkalinity, and calcium hardness about once a month. During a SLAM, test free chlorine several times a day. The more the pool is stressed, the more often you test.
Taylor K-2005 vs K-2006 — what's the difference?
They look nearly identical and test the same numbers (chlorine, pH, TA, CH, CYA) — the difference is the chlorine method, and it's the whole ballgame. The K-2005 uses the DPD color-match block: you compare a pink shade by eye, it tops out around 5 ppm, and it can't measure the high free-chlorine levels a SLAM requires. The K-2006 uses FAS-DPD drop titration: you count drops to a clear endpoint, it resolves to 0.2–0.5 ppm, and it reads chlorine all the way up to shock levels. If you ever have to clear algae, the K-2005 leaves you blind at exactly the moment you need numbers. Buy the K-2006 — same brand, same everything else, and the chlorine test actually works when it matters.
Why does the pool store get my CYA wrong?
It's less a bias than a dice roll: pool-store machines are inconsistent on CYA — owners who split one jar of water across two or three stores on the same day report answers as much as 100 ppm apart. CYA is the single number that sets your correct chlorine target, so a wrong reading in either direction quietly wrecks your dosing: reads low and you starve the chlorine (green pool, 'fine' numbers); reads high and you chase chlorine you don't need. A drop-based kit's real advantage is repeatability — the same water gives the same answer. Test your own CYA.