Figures also show 2025 is already on track to be even worse, with 93 notices issued so far - higher than the total number for both 2022 (42) and 2023 (43) combined.
Experts say the sudden spike should ring alarm bells for the government and regulators. Professor Nick Voulvoulis, an environmental technology expert at Imperial College London, warned: "Many of the contaminants involved, from nitrates to PFAS, reflect long-standing pressures on our water environment that current treatment systems were never designed to handle. PFAS, the so-called 'forever chemicals', persist in soil and water for decades and build up in the human body, with links to cancers, thyroid disease, and weakened immune response. The UK still relies on advisory guidance rather than legally binding limits for PFAS, leaving a major regulatory gap."
A major driver of the contamination alerts was linked to microbial breaches. In one of the most serious incidents, a damaged air valve allowed cryptosporidium - a parasite that causes severe diarrhoea - to enter a reservoir serving thousands of homes.
More than 17,000 households were left without safe water and many people fell ill.
Water suppliers also issued notices after detecting E. coli and coliform bacteria, both of which can cause serious stomach problems.