Alkalinity
A measure of water's capacity to neutralise acids, primarily from dissolved bicarbonate, carbonate, and hydroxide ions.
Alkalinity measures water’s buffering capacity — its ability to resist changes in pH when acids are added. It is mainly determined by the concentration of bicarbonate (HCO3-), carbonate (CO32-), and hydroxide (OH-) ions.
Why it matters
There is no ADWG health guideline for alkalinity, but it is operationally important:
- pH stability: Higher alkalinity means the water’s pH is more stable and resistant to sudden changes
- Corrosion control: Low-alkalinity water is more corrosive to pipes and plumbing
- Treatment optimisation: Water utilities adjust alkalinity to maintain effective disinfection and minimise pipe corrosion
Relationship to hardness
Alkalinity and hardness often occur together because both are influenced by dissolved calcium and magnesium carbonates. However, they measure different things: hardness measures mineral content, alkalinity measures acid-neutralising capacity.
Check Your Water
See how alkalinity levels compare in your suburb with real water quality data.
Disclaimer: Glossary definitions are provided for general educational purposes only and do not constitute medical advice or professional guidance. For specific health concerns about your drinking water, consult a qualified health professional. See our Terms of Use.