# pH buffer

> A pH buffer is a solution containing a weak acid and its conjugate base that resists pH change; in growing it means calibration buffers or water chemistry that stabilises pH.

- Canonical: https://genetixbay.com/knowledge/glossary/ph-buffer.html
- Also written: buffer solution, buffer, pH buffering agent, pH stabiliser, pH stabilizer
- Glossary category: pH, EC and water · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

In chemistry, a buffer is a mixture of a weak acid and its conjugate base (or a weak base and its conjugate acid) that holds [pH](https://genetixbay.com/knowledge/glossary/ph.md) nearly constant when small amounts of acid or base are added. Growers use the word in two ways. Calibration buffers are standard solutions at pH 4.01, 7.00 and 10.01 used to calibrate meters. Root-zone or water buffers are chemical systems, chiefly bicarbonate and carbonate in water and [phosphate](https://genetixbay.com/knowledge/glossary/phosphate.md) in some nutrient mixes, that keep a solution from swinging.

## In practice

Bicarbonate is the main natural buffer in [tap water](https://genetixbay.com/knowledge/glossary/tap-water.md). Some is helpful: around 30–60 ppm (mg/L) as CaCO3 [alkalinity](https://genetixbay.com/knowledge/glossary/alkalinity.md) steadies pH in hydro. Too much forces constant acid dosing and pushes pH up in the [root zone](https://genetixbay.com/knowledge/glossary/root-zone.md) over time.

Commercial "pH stabiliser" products are usually buffer blends. They can reduce drift but add their own ions; know what is in them. Calibration buffers degrade once opened and absorb [CO2](https://genetixbay.com/knowledge/glossary/co2-enrichment.md) (the pH 10 buffer especially); replace them regularly and never pour used buffer back into the bottle.

## Don't confuse with

- **Coco buffering**: pre-treating [coco coir](https://genetixbay.com/knowledge/glossary/coco-coir.md) with calcium and magnesium to load its exchange sites; a different meaning.
- **Buffering capacity**: how much buffer is present.

## Related terms

[Buffering capacity](https://genetixbay.com/knowledge/glossary/buffering-capacity.md), [Calibration solution](https://genetixbay.com/knowledge/glossary/calibration-solution.md), [Alkalinity](https://genetixbay.com/knowledge/glossary/alkalinity.md), [pH drift](https://genetixbay.com/knowledge/glossary/ph-drift.md)

## Read more

- [pH and EC meter calibration: buffers, slope, storage and when to replace a probe](https://genetixbay.com/knowledge/ph-ec/meter-calibration.md)
- [pH drift in hydro: why reservoir pH rises (and sometimes falls)](https://genetixbay.com/knowledge/ph-ec/ph-drift-hydro.md)

## Sources

1. Bugbee B. 2004. Nutrient management in recirculating hydroponic culture. Acta Horticulturae 648:99-112. https://www.ishs.org/ishs-article/648_12