pH of Tap Water UK: What It Means & Why It Matters
What is Water pH?
pH stands for "potential of hydrogen" and measures how acidic or alkaline your water is on a scale of 0-14. Pure water has a pH of 7.0 (neutral). UK tap water is typically slightly alkaline at pH 7.0-8.0.
UK Legal Limits
The DWI requires tap water pH to be between 6.5 and 9.5. Water companies carefully control pH at the treatment works because it affects pipe corrosion and the effectiveness of disinfection.
Why pH Matters
For Your Plumbing
Low pH (acidic) water corrodes copper and lead pipes, increasing the amount of metals that dissolve into your water. This is why water companies raise pH in areas with soft, naturally acidic water.
For Coffee
Water pH significantly affects coffee extraction. The Speciality Coffee Association recommends water at pH 6.5-7.5 for optimal flavour. If your water is above pH 8, it can make coffee taste flat. Many coffee enthusiasts use filtered water to bring pH into the ideal range.
For Aquariums
Fish are sensitive to pH. Most tropical fish thrive at pH 6.5-7.5, African cichlids prefer pH 7.8-8.5, and marine fish need pH 8.0-8.4. Your tap water pH determines which species are easiest to keep without constant adjustment.
For Plants
Most houseplants and garden plants prefer slightly acidic water (pH 6.0-7.0). Very alkaline tap water (above pH 8) can cause nutrient lockout in acid-loving plants like azaleas, blueberries, and rhododendrons.
Check Your Water's pH
Enter your postcode on WaterGrade to see the pH of your tap water, along with other quality parameters.