A blue colour in drinking water is rare but when it happens it is due to corrosion of copper plumbing.
The occurrence of a blue colour in drinking water is uncommon, but when it does happen, it is typically due to the corrosion of copper plumbing. This blue hue indicates elevated levels of copper in the water, a problem mainly observed in relatively new copper plumbing systems. Running the tap usually resolves the issue by eliminating the blue colour. If the colour persists however, it is advisable to contact your water company for an inspection of your plumbing. The water company can conduct tests on your water and offer guidance on improving water quality.
While copper is an essential nutrient, consuming very high levels can lead to stomach upsets (copper poisoning). However, water at these levels not only looks and tastes unpleasant but is also likely to be rejected by consumers. The drinking water standard is set at 2 mg/l, well below the threshold for affecting water quality or causing health issues.
Blue water is typically a result of unsuitable plumbing practices, such as the use of excess or incorrect flux when joining pipes and fittings. Stagnation of water in newly installed pipes before property occupation is another risk factor. Recorded cases often involve large public buildings or new housing estates. Qualified plumbers and water company-approved contractors, adhering to approved materials and procedures, are less likely to cause blue water issues.
This issue is more common in hard water areas where new copper pipes are installed in kitchens and bathrooms. In the initial weeks of use, the hardness scale may exhibit a blue/green color, which typically resolves as the plumbing settles and conditions. Keeping new plumbing in daily use and avoiding prolonged standing of water in pipes helps minimize the problem. Household anti-scaling cleaning products can be used to remove the blue-colored deposits.