Calibration issues with PH-1-3-2927 Probe for ZODIAC PH EXPERT: Solutions and Technical Support

Client:
Hello, you sent me a probe Ref. PH-1-3-2927 for ZODIAC PH EXPERT. It constantly indicates a pH value of 5.3. It has been calibrated according to ZODIAC instructions. The water here is hard, well above 7.4 which requires a lower pH liquid. Do you have an explanation? Raymond MONNERY - FA 009709

Technical Advisor:
It may be a probe problem. Please do this quick test https://ph-redox-pool.com/gb/content/16-ma-sonde-ph-est-elle-hors-service-.

Technical Advisor:
Give me the result, we will replace it if it's the problem.