How to Test Pool Water
Accurate water testing is the foundation of proper pool maintenance. Learn the best techniques for reliable results.
Testing Methods Compared
| Method | Pros | Cons | Best For |
|---|---|---|---|
| Test Strips | Fast, easy, inexpensive, tests multiple parameters at once | Less accurate, can be affected by storage, subjective color reading | Quick daily/weekly checks |
| Liquid Test Kit (DPD) | More accurate, consistent results, longer shelf life | Takes longer, requires counting drops, tests one parameter at a time | Weekly testing, troubleshooting |
| Digital Tester | Most accurate, easy to read, no color matching | Higher cost, requires calibration, batteries needed | Frequent testing, precision needs |
Using Test Strips Correctly
Test strips are the most common method for home pool testing. Follow these steps for the most accurate results:
1. Store strips properly: Keep in a cool, dry place away from direct sunlight. Never store in the pool area where humidity can affect them. Close the container immediately after use.
2. Collect water correctly: Dip your arm elbow-deep into the pool, away from return jets and skimmers. Collect water from at least 18 inches below the surface.
3. Dip the strip: Submerge the entire strip for 2-3 seconds (or as directed). Don't shake or swirl - a quick dip works best.
4. Remove and wait: Hold the strip horizontally (not dripping) and wait the exact time specified on the bottle (usually 15-30 seconds). Don't wait too long as colors continue to develop.
5. Compare colors: Match colors in good lighting (not direct sunlight). Compare while holding next to the color chart. Read quickly - colors fade over time.
Using Liquid Test Kits (DPD/Taylor)
Liquid test kits provide more accurate results but require careful technique:
Chlorine Testing (DPD):
1. Rinse test cell with pool water
2. Fill to the mark with pool water
3. Add reagent drops (exact number specified)
4. Cap and invert to mix
5. Compare color to chart (pink scale)
6. For combined chlorine, add DPD #3 reagent
pH Testing:
1. Rinse test cell with pool water
2. Fill to the mark
3. Add phenol red reagent drops
4. Cap and invert gently
5. Compare to color chart (yellow to red scale)
6. High chlorine can bleach the color - dilute if needed
Testing Schedule
2-3 Times Per Week:
• Free chlorine
• pH level
• Combined chlorine (if issues present)
Weekly:
• Total alkalinity
• Cyanuric acid (during season)
Monthly:
• Calcium hardness
• Total dissolved solids (TDS)
• Metals (iron, copper)
Test More Often When:
• Heavy pool use
• After rain or storms
• During hot weather
• After adding chemicals
• Testing near return jets (skews readings)
• Using expired test strips or reagents
• Not waiting the correct time before reading
• Testing in poor lighting
• Contaminating reagents by touching dropper tips
• Not rinsing test cells between tests
• Testing immediately after adding chemicals (wait 4+ hours)
• Testing surface water instead of 12-18" deep
Proper Sample Collection
Where and how you collect your water sample significantly affects accuracy:
Good Sample Locations:
• Center of pool
• 12-18 inches below surface
• Away from skimmers and returns
• Multiple locations (average results)
Avoid These Locations:
• Right at return jets
• Near skimmer openings
• Surface water only
• Dead spots with poor circulation
Interpreting Your Results
After testing, compare your results to these ideal ranges:
| Parameter | Ideal Range | Action if Low | Action if High |
|---|---|---|---|
| Free Chlorine | 2-4 ppm | Add chlorine | Wait or add sodium thiosulfate |
| pH | 7.4-7.6 | Add pH increaser (soda ash) | Add pH decreaser (muriatic acid) |
| Alkalinity | 80-120 ppm | Add baking soda | Add muriatic acid |
| CYA | 30-50 ppm | Add stabilizer | Dilute (partial drain) |
| Calcium | 200-400 ppm | Add calcium chloride | Dilute or use sequestrant |
Pro Tips for Accurate Testing
• Take your pool store water sample from the same depth and location you test at home for consistent comparison
• Keep a log of your test results to identify trends and patterns
• Replace test strips and reagents annually for accuracy
• Consider getting a Taylor K-2006 kit for the most accurate home testing