Testing Guide
Testing your pool water is the most important thing you can do as a pool owner. You cannot fix what you cannot measure. Here is what to test, how to do it, and what to do with the results.
Not all tests need to happen at the same frequency. Some things change daily, others change slowly over weeks. Here is the priority order.
This is the chlorine that is actively sanitizing your water. If free chlorine drops below 1 ppm, bacteria and algae can take over within hours. Test this first because it is the most critical reading.
pH affects how well your chlorine works and how comfortable the water feels. At pH 7.2, about 63% of your chlorine is active. At pH 8.0, only about 21% is active. The same amount of chlorine is dramatically less effective at high pH.
Alkalinity is a buffer that prevents pH from swinging wildly. If TA is too low, your pH will bounce around and be hard to control. Adjust TA before trying to fine-tune pH.
Protects chlorine from sunlight but reduces its effectiveness when too high. CYA only leaves the pool through water replacement, so it accumulates over time. What to do when CYA is too high.
Too low and the water becomes corrosive, damaging surfaces and equipment. Too high and calcium deposits form on tile, heaters, and salt cells. Hard to adjust quickly, so test monthly and address trends early.
Dip a strip in the water, compare the color pads to a chart. Quick and easy. Results are approximate, not precise. Good enough for routine checks.
Best for: Casual weekly monitoring. New pool owners who want something simple.
Cost: About $10-15 for 50-100 strips.
Add reagent drops to a water sample and compare colors or count drops until a color change occurs. More accurate than strips. The Taylor K-2006 is the gold standard.
Best for: Accurate readings when adjusting chemistry. Troubleshooting problems.
Cost: $50-80 for a comprehensive kit (lasts a full season).
Where and how you collect the sample matters. Do not scoop from the surface or near a return jet. Plunge the collection bottle or tube elbow-deep, about 12-18 inches below the surface, away from skimmers and returns. This gives you a representative sample.
Test the sample within a few minutes of collecting it. Chlorine degrades quickly in a small sample, especially in sunlight. If you are bringing a sample to a pool store, keep it sealed and out of direct sun.
Test at the same time each week for consistent results. Late afternoon after the pool has been running all day gives a good snapshot of your typical chemistry.
Testing is only useful if you act on the results. The most common adjustments are adding chlorine (low FC), adding muriatic acid or dry acid (high pH), adding baking soda (low alkalinity), and shocking (combined chlorine is high).
Pool Clarity takes the guesswork out of this. Log your test results in the app, and it tells you exactly what chemicals to add and how much based on your pool volume.
Pool Clarity tracks every test, shows trends, and recommends exact chemical dosages. Free to use.