Bluelab pH 4.0 Calibration Solution 250ml - Carton of 6

Accurate pH Readings Start With Calibration, 250 ml x 6

pH probes drift as they age and collect residue, so readings slowly move away from the truth. Calibrating against known references realigns the probe. pH 4.0 is the second reference point in Bluelab's standard 2-point calibration, used after pH 7.0.

Six 250 ml bottles suit home growers and small teams who calibrate monthly and want fresh solution through the season.

Key Features & Benefits

• Carton of 6 — six 250 ml / 8.4 fl oz bottles.
• Bluelab reference solution — for the second point in a 2-point pH calibration, after pH 7.0.
• Longer probe life — regular calibration and care help pH and EC products last.
• Stock for the season — a carton keeps fresh solution on hand for routine maintenance.

Who Should Use Bluelab pH 4.0 solution

Growers who use Bluelab or other pH meters and want fresh solution for routine care, from home growers to commercial teams maintaining many probes.

About Bluelab pH 4.0 Calibration Solution

Bluelab makes its pH 4.0 Calibration Solution as part of its probe care range. Bluelab states there is no applicable warranty for solution products.

Frequently Asked Questions

Why calibrate with both pH 7.0 and pH 4.0?

Two reference points let the meter correct both its offset and its slope, which keeps readings accurate across the range plants use. Bluelab's standard 2-point calibration uses pH 7.0 first, then pH 4.0 (or pH 10.0).

How often should I calibrate?

Many Bluelab pH meters show a 30-day reminder, which is a good baseline. Recalibrate sooner if readings drift or after cleaning the probe.

Can I reuse calibration solution?

Pour what you need into a clean cup and discard it after use. Pouring used solution back contaminates the bottle and shifts its value.

Does pH 4.0 work with other brands' meters?

pH 4.0 is a standard calibration point used by most pH meters. Follow your meter's calibration instructions.