Domakihub How to Read Pool Test Strips and Keep Your Water Balanced
Dip, wait, match — and know exactly what to do next.
Reviewed by Domakihub pool pros · 2026-06-23 · 4 min read
Pool test strips are the fastest way to know whether your water is safe, clear, and comfortable — a must for anyone managing a home pool, a holiday villa, or a hotel facility in Greece where the summer heat puts chemistry under constant stress. The Swim University video above shows the technique in real time; this guide walks you through every reading in order so you can act on the results straight away. Get the habit right once and balanced water becomes a five-minute routine.
Why Test Strip Readings Go Wrong
Most errors happen before the strip even touches the water. Wet hands, an uncapped tube left in direct sun, or strips past their expiry date all produce false colours that lead to over- or under-dosing chemicals. In the Greek summer, UV light fades the reagent pads faster than in cooler climates, so always store strips in a cool, dry place and check the expiry date each season.
Reading the colours in bright sunlight is another common mistake. Take the strip into the shade or hold it so the pads face away from the sun. Comparing a washed-out pad against the chart in full glare can make a 3.0 ppm chlorine reading look like 1.0 ppm and send you reaching for chemicals you do not need.
What Each Colour Band Is Measuring
A standard 6- or 7-way strip tests for free chlorine, pH, total alkalinity, cyanuric acid (stabiliser), total hardness, and sometimes bromine or iron. Each pad reacts with one parameter and changes to a colour that maps to a specific level on the bottle's chart. Understanding what each parameter actually controls helps you prioritise: pH and chlorine affect swimmer safety most immediately, while alkalinity and stabiliser protect your dosing from swinging wildly day to day.
For pools in Greece, cyanuric acid deserves extra attention. Strong UV sunlight degrades unstabilised chlorine within hours, so stabiliser levels between 30–50 ppm are standard. If your strip shows stabiliser above 80 ppm, however, chlorine becomes less effective even when its reading looks good — a condition sometimes called chlorine lock.
How to Read Pool Test Strips: 5 Steps
- 1
Collect the water sample correctly
Use a clean, dry hand to hold the strip. Submerge it elbow-deep (roughly 40–50 cm below the surface) away from return jets and skimmers — surface water and jet-turbulence give unrepresentative readings. Hold the strip in the water for exactly the time shown on your strip packaging, usually 1–2 seconds; do not swirl it.
- 2
Hold it flat and wait the full reaction time
Remove the strip and hold it horizontally, pad-side up, in a shaded spot. Do not shake the water off — that washes reagent from the pads. Wait the time printed on the label (commonly 15–30 seconds for chlorine pads, up to 60 seconds for hardness). Starting colour comparisons too early is the single biggest cause of wrong readings.
- 3
Compare pads to the chart in the correct order
Read from left to right or bottom to top exactly as the bottle shows — the manufacturer prints them in that sequence for a reason (some pads continue developing and need the last read). Hold the strip next to the chart at the same horizontal height and match each colour to the nearest band. If a pad falls between two bands, note both values and use the average.
- 4
Record every reading before taking action
Write down all six or seven values before you adjust anything. Changing one parameter affects others: raising alkalinity nudges pH upward, adding calcium hardness can cloud the water if phosphates are present. Having a written baseline for each test session also shows trends over time — a pool that needs heavy chlorine top-ups every two days in July may have a stabiliser or filtration problem, not just a demand spike.
- 5
Adjust one parameter at a time and re-test after 4 hours
Dose for the most critical out-of-range reading first (usually pH, because it controls how effective chlorine is), run the pump for at least four hours to circulate the chemical, then re-test before adding anything else. In high-heat conditions typical of Greek summers, chlorine can drop by 1–2 ppm between morning and afternoon, so test at the same time of day each day for comparable results.
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FAQ
- How often should I test my pool with strips?
- During the swimming season in Greece, test at least twice a week — ideally every day when daytime temperatures exceed 30 °C or after heavy use, rain, or a backwash. In cooler months or when the pool is covered, once a week is usually sufficient.
- My test strip shows no colour change on the chlorine pad — is the chlorine too high or too low?
- Both extremes can cause a blank or washed-out pad. Very high chlorine (above roughly 10 ppm) bleaches the reagent, giving a false zero. Try diluting your sample 50/50 with distilled water, re-testing, then doubling the reading. If the pool smells strongly of chlorine and the pad is blank, over-chlorination is the likely cause.
- Can I trust test strips as much as a liquid test kit?
- Strips are accurate enough for day-to-day maintenance when used correctly and within their expiry date. For precise monthly baseline readings — especially cyanuric acid and total hardness, which require titration — a drop-based liquid kit or a professional lab test gives more reliable numbers. Many pool professionals use strips for daily monitoring and liquid kits for their weekly deep check.