How to Test Your Pool Water (and Why Strips Lie to You)

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

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:

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

Nobody needs this, but it’s the nicest $43 in pool testing

Everything above changes what you know. This one only changes how it feels — and we’re putting it here because it’s genuinely delightful, not because your water needs it.

A drop-count test asks you to add a drop, swirl the vial, look, and repeat, over and over, while watching for a colour change that arrives gradually. A magnetic stirrer takes the swirling off your hands: a little bar spins in the vial at 600 RPM so the sample is always evenly mixed, and a lit base puts the colour change right in front of you. You drop with one hand and watch with both eyes. That’s the whole pitch.

Be clear about what it does not do: it will not make your results more accurate. A FAS-DPD test hand- swirled properly gives you exactly the same numbers. If you test once a month, skip it without a second thought. If you’re mid-SLAM and running the chlorine test several times a day, it stops being a gadget and starts being the reason testing doesn’t feel like a chore.

It’s also the lowest-rated thing we recommend on this page, and honestly so — at 4.0★ the recurring complaint is build quality for the money. It’s a $43 plastic box that spins a magnet, and it feels like one. We’re recommending it anyway, as a luxury, with that caveat attached.

“This thing is great if you test your pool water often, and you use the drip count method. Not cheap, so it’s kind of a luxury item, but I will not likely go without one again.” — chandler, az, verified owner · Amazon

That’s the honest verdict from an owner who gave it four stars, and it’s ours too: a luxury item you won’t want to give back.

The kit doesn’t wear out — the reagents do

A K-2006 is a plastic case, a few graduated tubes and nine bottles. Nothing in it breaks. What happens instead is that the bottles empty, and they do not empty evenly.

The chlorine reagents go first, by a wide margin. R-0870 (the DPD powder) and R-0871 (the FAS titrant) are consumed on every chlorine test, and chlorine is the number you test most — daily in season, and several times a day during a SLAM, which can run a fresh bottle down inside a week. Meanwhile the pH, alkalinity, calcium and CYA reagents are barely touched, because you test those weekly at most. So the failure mode is not “my kit ran out,” it’s “my chlorine reagents ran out and the other seven bottles are nearly full.” Buying a second complete kit to get at two bottles is the expensive way to solve that.

Buy the two bottles separately and you get more, for less, on better evidence. The combined refill kit is the convenient answer, but it is not the sharp one. A 16 oz bottle of R-0871 titrant costs about $34.48 — roughly the same as the refill kit, which contains 2 oz of that same titrant plus the powder. Bought separately, the powder is about $12.26. The ratings run the same direction: 1,212 owners have rated the powder and 401 the big titrant, against 45 for the combined kit.

So: if you test chlorine daily in season, run a SLAM, or use the 25 ml sample that makes the FAS-DPD result repeatable, buy the bottles. If you test weekly and want one thing in the cart, the refill kit is fine and you are paying a few dollars for that.

The other half of this is age, and it catches people who never ran out at all. Taylor states its reagents are “formulated to remain effective for at least one year” and that “it is a good practice to replace your test reagents in the beginning of each pool season.” Reagents that sat through a winter in a hot shed or a freezing garage are outside the storage range Taylor specifies — “a consistent temperature in the range of 36°–85°F” — and a kit that suddenly reads strangely in April is usually old reagents, not a broken kit or a broken pool.

Taylor’s own tell for a reagent that has gone off: “A reagent is suspect if it is not the color that you are used to seeing or if it has changed color significantly over time,” and new floating particles that will not dissolve when shaken are the other sign. If your chlorine reagents are over a year old, replace them before you spend a weekend chasing a reading.

If everything in the kit is that old — not just the chlorine pair — buy the complete K-2006 refill set instead of this one, because the same argument applies in reverse: refilling two bottles does not fix seven.

The salt kit empties the same way, only faster

If you run a K-1766 for salt, the same rule applies and the split is even more lopsided. The test is a titration: one drop of R-0718 silver nitrate reads 200 ppm, so a pool sitting at a normal 3,200 ppm consumes about sixteen drops every time you test. The R-0630 chromate indicator beside it is a fixed few drops per test no matter how salty the water is. One bottle drains roughly three times faster than the other — and it is also the one that costs twice as much.

There is a second failure mode here that has nothing to do with running out. R-0718 is light-sensitive, and Taylor specifies storing it cool and dark. A bottle kept on a sunny shelf will keep dispensing drops long after it has stopped being accurate, which reads as a pool whose salt level mysteriously drifted.

If your salt readings have gone strange, replace the silver nitrate before you replace the kit, and check where you have been keeping it before you replace anything.

Running each test, on one screen

The K-2006’s own instructions are two dense sheets, and the single most common complaint from owners is that the manual isn’t written for a normal person. It isn’t — but the tests themselves are short. Here is the whole kit, condensed from Taylor’s own instruction sheet (#5165), in the order you’ll actually run them.

When a level is too high to titrate, switch to the small sample and the matching multiplier: chlorine goes to a 10 mL sample at 0.5 ppm per drop; alkalinity to 10 mL, 1 drop R-0007, 3 drops R-0008, × 25; hardness to 10 mL, 10 drops R-0010, 3 drops R-0011L, × 25.

To raise or lower pH, don’t guess the dose — keep the treated pH sample and add R-0006 (base demand) or R-0005 (acid demand) drop by drop until you hit the pH you want, then put that drop count into the chemical calculator.

If your kit came with the little syringe

Some Taylor kits ship a syringe titrator (part 6250, with its own instruction sheet #5056) instead of leaving you to count drops. It is worth understanding what it is for, because it is easy to assume it belongs to the hardness test: it doesn’t. It is only for the FAS-DPD chlorine tests — Taylor’s own classification lists exactly two uses for it, free chlorine and combined chlorine. Calcium hardness still means counting 20 drops of R-0010 by hand.

Fill it to the 1.0 mL mark with R-0871 — the titrating reagent, not pool water — dispense slowly into the swirling sample until the pink goes, then hold it tip-up and read where the plunger seal sits. 1 mL of R-0871 = 5 ppm of chlorine, so the arithmetic is just:

ppm chlorine = (1.00 − the mark you stopped at) × 5

Stop at 0.34 and you have 3.3 ppm. Refill and keep going if the pink is still there, adding 5 ppm for every refill. Then refill to 1.0 mL, add your 5 drops of R-0003, and repeat for combined chlorine.

It is the fix for the one genuinely tedious part of this kit: a SLAM-level chlorine test is dozens of counted drops, and this reads the whole thing off one plunger position instead. You lose nothing for it — the syringe resolves to 0.1 ppm against 0.2 ppm per drop.

What it does NOT test: metals

One honest limit on the kit above, because we send readers to it constantly and it is easy to assume it covers everything: the K-2006 does not test for metals. No standard drop kit does. Copper and iron are not part of the five numbers, and for most pools that is fine — until it isn’t.

It matters in three situations: you fill from a well (the classic iron carrier), you run or have run a copper-based algaecide or mineral system, or you have a stain and need to know which metal it is before treating it — because the standard treatment is for iron and makes copper stains worse.

This is a screening tool rather than a precision instrument, and metals are the second deliberate exception to our drop-test-over-strips rule, alongside salt: no practical consumer drop test reads both, and the answer decides which treatment to run rather than a dose to calculate. Know where its limit falls before you rely on it: an owner who cross-checks against a commercial lab says it reads closest to his lab’s iron figures of anything he uses, and still cannot resolve the 0.1 ppm left in his water after treatment — below about 1 ppm you get “not zero, and not over 1,” which is a yes/no rather than a number. That is enough to pick a treatment and not enough to track a trace level down. Test your fill water with it too — that is usually where the metal comes from, and it is the cheapest possible time to find out. Full procedure: how to remove metal stains.

How to test (the fast version)

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.