Bluelab pH 4 & 7 Calibration Solutions

pH Probes should be routinely cleaned and calibrated using Bluelab pH 4 & 7 Calibration Solutions to ensure the highest level of accuracy.

Serious commercial growers should clean and calibrate their pH probes every 1 – 2 weeks.

Some growers may need to do this procedure more frequently.

The frequency of cleaning and calibration that is required is all dependent on the cleanliness of the hydroponic system and the type of crop which is being grown.

Growers who regularly dump their tanks and do not have a high organic loading in their systems don’t need to clean and calibrate their probes quite as often as those who accumulate organic matter such as root matter, leaf material or algae in their systems or who use nutrient solutions or additives which are oily or have impurities.

The easiest way to set the interval for the cleaning and calibration of probes is to allow the system to run as normal and then periodically check the pH probes in pH 4 & 7 Calibration solution to see if they are maintaining their accuracy.

The calibration solutions always provide an accurate reference point.

A pH probe should always read 7 when dipped in a pH 7 calibration solution and it should always read 4 when dipped in pH 4 calibration solution.

If the readings are different to the calibration solutions then this indicates that calibration or cleaning of a probe is required.

If the probes are identified as losing their accuracy after 7, 10 or 14 days or more, then that should be the regular interval set for cleaning and calibrating the probes.

Pure Hydroponics supplies the Bluelab range of Calibration Solutions:

  • pH 4 x 250ml Bottle – NZ$15.83 + GST

  • pH7 x 250ml Bottle – NZ$15.83 + GST

  • pH 4 x 500ml Bottle – NZ$28.83 + GST

  • pH7 x 500ml Bottle – NZ$28.83 + GST

  • Wholesale Pricing is Available for Retailers 


Simply tip a small quantity of each solution into a separate glass or container. Clean the tip of the pH probe as directed and rinse well.

Dip the probe tip into the pH 7, 4 solution for testing accuracy (making sure to rinse between different solutions) or follow the calibration instructions if you intend to calibrate the meter.

After the sample of calibration solution is used once, tip it out (not back into the bottle) and use a fresh sample of solution from the bottle for the next test/calibration.

Bluelab pH Probe – Probe Care Instructions