Abstract: To test water quality at home, a single multi-parameter water test pen is enough for daily preliminary screening: first calibrate with purified water, fill a cup and let it sit, insert the probe at an angle, remove air bubbles, tap to test, then read the interpretation. This article uses the Water Detective 9 parameter version as an example.
Keywords: how to test water quality at home, self-testing tap water quality, home water quality testing methods, how to use Water Detective
One-sentence answer: To test tap water at home, the easiest way is to use a multi-parameter test pen that can measure turbidity, organic matter and TDS, following five steps: "calibrate—fill water and let it sit—insert into water to test—read the interpretation—retest regularly." The Water Detective 9 parameter version produces 9 results at once, and the AI in the mini program will directly tell you how the water is and what to do.
Step 1: Calibrate with purified water
Calibrate before first use, because transport vibration may cause deviation. Use purified water such as C'estbon, Wahaha, green-bottle Nongfu, or Watsons distilled water; do not use mineral water, bottled water or water from a water purifier. On the Water Detective, long-press the M key for about 5 seconds to enter calibration, or tap calibration in the mini program. After calibration, test the purified water again; if TDS, TOC and COD are close to 0, calibration is complete.
Step 2: Fill water and let it sit for a while
Fill a clean cup with water and let it sit for a short while so residual chlorine and bubbles can dissipate. The most suitable water temperature is between 10-40℃; freshly boiled water or ice water should be left until it returns to room temperature.
Step 3: Insert the probe at an angle to expel air bubbles
Remove the white outer cover and first rinse the probe with the water to be tested. Insert the probe into the water at an angle, gently swirl it or tap the cup wall to drive away bubbles. Bubbles are the most common cause of readings fluctuating up and down.
Step 4: Tap to test and check the screen and mini program
Lightly tap the M key to start testing. The pen's color screen first displays a radar chart and overall score (100-point scale, four levels: excellent/good/medium/poor); turn pages to view each value, with each indicator changing color separately. Turn on Bluetooth and location on your phone, and the WeChat mini program "比特原子水侦探" automatically syncs the results without pairing.
Step 5: Read the AI interpretation and retest regularly
The AI in the mini program analyzes which item in this cup of water is high, possible causes and suggestions. It is recommended to repeatedly compare these situations: the first cup in the morning versus after running the water, before and after a water outage, rainy season versus dry season, and different faucets. With more records, whether your home water quality has changed becomes clear at a glance.
Common reference values for tap water
| Indicator | Typical range | Description |
|---|---|---|
| TDS | Approx. 100-200 ppm | Higher in the north; in places such as Shenzhen it is often below 100 |
| COD | Approx. 0.8-2.5 mg/L | A higher value indicates increased organic load |
| TOC | Approx. 1.0-3.0 mg/L | Total organic matter |
| Turbidity | National standard limit no more than 1 NTU | Household test results are for reference only |
| UV254 | No unified national standard; recommended ≤0.03 | A higher value suggests more organic matter |
Frequently Asked Questions
Q: Why are the readings higher after boiling the water? When water evaporates, the substances in it become concentrated, just like porridge gets thicker the longer it cooks. Boiling does not mean all indicators are normal.
Q: Why do two measurements of the same cup of water differ? First check whether there are bubbles. When repeating the measurement, keep the pen still and wait 10 seconds before measuring again; a TOC/COD difference within ±0.2 is normal.
Q: How often is it appropriate to measure? For routine use, measure once or twice a week; add extra measurements when the water supply is cut off, the filter is replaced, the water tank is cleaned, or the water's color or taste is abnormal.