Test pH and chlorine at least 2 to 3 times per week. Use test strips for quick daily checks and a DPD kit or digital tester for accurate weekly measurements. Test in the morning before use, not immediately after adding chemicals.
What parameters to test
| Parameter | Frequency | Ideal value |
|---|---|---|
| pH | 2-3x per week | 7.2 to 7.6 |
| Free chlorine | 2-3x per week | 1.0 to 3.0 mg/l |
| Total alkalinity | 1x per week | 80 to 120 mg/l |
| Calcium hardness | 1x per month | 200 to 400 mg/l |
| Cyanuric acid | 1x per month | 30 to 75 mg/l |
| Parameter | Ideal range | Unit | Frequency | Too low | Too high |
|---|---|---|---|---|---|
| pH level | 7.2 - 7.6 | 2-3x per week | Eye and skin irritation, corrosion of metal components | Chlorine up to 80% less effective, calcium scaling | |
| Free chlorine | 1 - 3 | mg/l (ppm) | 2-3x per week | Insufficient disinfection, algae growth | Eye and skin irritation, bleaching of swimwear |
| Total alkalinity | 80 - 120 | mg/l | 1x per week | pH fluctuates wildly, water becomes corrosive | pH difficult to adjust, cloudy water |
| Calcium hardness | 200 - 400 | mg/l | 1x per month | Water leaches calcium from walls, damage to concrete and plaster | Scale build-up on walls and equipment, cloudy water |
| Combined chlorine | 0 - 0.2 | mg/l | 1x per week | N/A | Unpleasant chlorine odour, irritation, reduced disinfection |
| Water temperature | 26 - 28 | °C | Daily (summer) | Less swimming comfort, chlorine acts more slowly | Accelerated algae growth, more chlorine needed |
Method 1: Test strips
Best for: quick daily checks.
How to use correctly:
- Dip a dry strip for exactly 1 second at 30 cm depth
- Remove and hold horizontally
- Wait exactly 15 seconds
- Compare colours with the scale in natural daylight
Common mistakes: holding the strip too long, reading in artificial light, using expired strips.
Method 2: DPD drop test
Best for: accurate weekly checks.
DPD (N,N-diethyl-p-phenylenediamine) reacts with free and combined chlorine. More accurate than strips but requires two hands and good colour vision. Gives separate readings for free and total chlorine.
Method 3: Digital tester
Best for: precise measurements, serious pool maintenance.
A digital pH meter reads to 0.01 accuracy. Calibrate every 2 to 4 weeks with pH 7.0 buffer solution.
When to test
Optimal: morning before first use, before the pump has run.
Always test: after rain, after heavy use, after topping up water, when the water looks suspicious, and before closing the pool for winter (see our winterizing checklist ).
Wait: 30 minutes after swimming, 4 hours after adding chemicals.
Where to take the water sample
Take the sample at 30 to 40 cm depth, at least 30 cm from the wall. Surface water gives a distorted reading, and water near the walls is not representative.
Test pH and chlorine at least 2 to 3 times per week. Test alkalinity weekly and calcium hardness monthly. In hot weather or after heavy use, test daily. Consistent testing is far easier than correcting a problem that has been building for several days.
