pH is a measure of acidity or alkalinity. The water quality regulations specify that the pH of tap water should be between 6.5 and 9.5. Water leaving our treatment works typically has a pH between 7 and 8, but this can change as it passes through the network of reservoirs and water mains.

If the pH of your water has changed, and yours is the only property affected, the source will be your internal pipework and plumbing. Possible sources include plumbed-in water filters or softeners, incorrectly installed washing machines or dishwashers, incorrect fittings and taps supplied from storage tanks. If you have had any recent work carried out on your plumbing then excessive use of solder or flux could be the cause. In this case the problem may improve over time, or you might want to consider changing the pipework or joints.

There are no health risks associated with consuming water that is slightly acidic or alkaline. After all, we can eat lemons and drink soft drinks. However, when the pH of the water is much lower than the standard it can lead to metals from plumbing and fixtures in properties to be released. This could cause a health problem. In these circumstances the water may have a slightly bitter or metallic taste. If the pH of your water is too high, it will have a taste similar to baking soda and have a slippery feel to it. It will also begin to leave scale deposits on plumbing and fixtures.

For more information, please take a look at our factsheet on pH (PDF 47 KB opens in a new window).