1. ph-redox-pool.com

To check if your pH probe is working, you can:

1) Dip the probe in a glass of water

2) Read the pH value

3) Add vinegar to the water

4) Read the pH value again

If the pH value drops by 1 or 2 pH units then your probe is most likely working.

Warning: If your probe is old. It may not take time!