How do I calibrate a pH probe?

The pH probe is the sensor with the chess bishop, or, castle tower looking end (Figure 1). Calibrating it in solution is required in between grows, as discussed HERE, and can be beneficial during a grow if your probe has bacteria build up. 

Fig 1. This is a Grobo pH probe. Pay attention to the end, as the EC probe's differs from what the pH probe's looks like.

Best Practices for Calibrating pH

Here are some best practices for when you must calibrate your pH probe:

1. You must have 7 and 4 calibration solutions to calibrate your pH probe (7 is HERE and 4 is HERE) You cannot calibrate this part without them.
2. Always have a recipe applied when you're calibrating your pH probe. 
3. Gently clean your pH probe before each calibration to ensure no bacteria build up is present. 
4. Do not do any other action during a calibration. This includes draining, filling, changing stage or recipe, or changing the light schedule. 
5. You cannot calibrate outside of the Grobo App (HERE and HERE). The calibration feature is available in the Maintenance menu for you to use. 

How to Calibrate pH

The Grobo App (HERE and HERE) has a calibration feature with easy-to-follow instructions. Here is a summary of the app's process:

1. Have on hand both calibration solutions, a glass filled with tap water, and two empty shot glasses.
2. Run the calibration feature, accessible via the Maintenance section on the leftmost side of the Grobo app.
3. Clean your pH probe with mild soap and water.
4. Place the pH probe in solution 7 at this time. Run the check to see if you match 7.
5. If your probe needs calibrating, you will fail this health check. Keep the probe in solution 7 to calibrate it to 7 at this time.
6. Once the app is done calibrating in 7, rinse your pH probe off in tap water.
7. The Grobo app will now ask you to put the probe into solution 4. Do so, and you will calibrate to 4 at this time.
8. This health check will then end.
9. Lastly, run the health check again to ensure you it calibrated correctly. You will put the probe in 7 solution and it should pass this check at the beginning, showing "Success!" If the app continually asks you to calibrate multiple times, your pH probe is likely expired and will need replacing. Go HERE to purchase a new pH probe from our site. 

The video HERE explains the process if you would like to see someone calibrate before trying.

Still have questions? Please see HERE for how to contact us.