Public splash parks and paddling pools, often a popular destination for families during hot weather, are facing scrutiny due to alarmingly high levels of bacteria found in their water. An investigation into six such facilities in and around London revealed that some had bacteria counts up to 100 times higher than the recommended guidelines, posing potential health risks to children.
Experts warn that vital checks of water quality and chlorine levels, crucial for disinfection, are being missed by some operators. These lapses leave children, whose immune systems are less developed, vulnerable to exposure from bugs like E. coli, norovirus, and Pseudomonas. Additionally, a parasite known as cryptosporidium, which causes severe gastrointestinal illness, is not routinely tested for.
The Pool Water Treatment Advisory Group (PWTAG) sets water quality standards used by health authorities and councils. According to PWTAG, chlorine levels in splash parks should be checked every two hours when open, as chlorine is consumed by contaminants like sweat, urine, feces, and skin cells. Sunlight can also reduce chlorine levels, particularly in busy outdoor pools on hot days. If chlorine levels drop too low, bacteria can multiply rapidly.
Concerns are amplified by children's hygiene habits, as they are more likely to ingest pool water. Some parents have been observed rinsing children's bottoms in the water after nappy changes, a practice that can introduce germs, while others allow children to drink directly from water jets.
The investigation, conducted on August 11 and 12, when temperatures ranged from the mid-20s to around 30C, collected samples from six facilities. Two sites had bacterial counts above PWTAG's 'unsatisfactory' level of 100 colony-forming units per millilitre (CFU/ml). Two others recorded counts 1,000 times higher. The total viable count (TVC) for two locations, Runnymede Pleasure Grounds and California Country Park, exceeded 10,000 CFU/ml.
While E. coli and coliforms, indicators of recent fecal contamination, were not detected in any of the samples, a high TVC can signal failing chlorination or the presence of bacteria in biofilms, which can accumulate in pipework. These biofilms can harbor bacteria like Staphylococci, which cause skin and wound infections and can survive even when E. coli is neutralized.
Some facilities, like Runnymede Pleasure Grounds and California Country Park, use automatic chlorine dosing systems, yet still experienced high bacteria levels. The PWTAG notes that financial pressures can limit the resources available for operators to conduct sufficient checks. The aging infrastructure of many public pools, with over 1,200 public pools in the UK reportedly over 40 years old, may also contribute to these issues.
Cryptosporidium presents another significant risk. This parasite is highly resistant to chlorine and can cause severe diarrhea, vomiting, and dehydration. In England, between 2023 and 2025, 14 outbreaks linked to swimming pools or water parks affected at least 86 people. However, crypto is not routinely tested for, with current UK policy focusing on testing during outbreaks or suspected filtration failures.
Experts suggest that proactive testing of high-risk pools, particularly children's pools, could be more effective. They also advocate for improved water treatment methods, such as enhanced filtration and ultraviolet or ozone treatment, to remove cryptosporidium and other pathogens more effectively. While routine testing for crypto is difficult and expensive, improved physical filtration and UV or ozone treatment are considered more cost-effective long-term solutions.
Despite these findings, health experts emphasize that parents should not be deterred from using splash parks. Local authorities are responding to the investigation's findings. Runnymede Council, which had been aware of fluctuating water quality during the heatwave, commissioned independent tests and temporarily closed the pool. Wokingham Borough Council stated that its pool's pH and chlorine levels remained within recommended ranges and announced a shock chlorine treatment and further microbial testing.