Standard pool operating procedures were not followed an investigation has concluded, when a norovirus outbreak led to 120 people falling ill.

Children and adults caught the vomiting bug after visiting Splashes in Rainham on Friday, October 28 last year.

Public Health England launched an investigation and today, it was revealed that Medway Council's own standard pool operation procedures were not met on the day.

The investigation confirmed chlorine levels in the pool at the start of the day were within the council’s normal operating procedure guidelines – at a level which means norovirus should not have been able to spread in the water.

Further checks were not formally recorded by staff after 2pm however, and it was not clear whether chlorine levels were maintained above recommended levels for this period.

PHE has concluded it was not possible to identify how or where norovirus was introduced or spread during the affected period.

The council have disputed the figure and say they had 31 reports equating to around 60 individual cases, but a count on Facebook by one of those affected suggests it was around 120 cases. PHE found 68 cases.

On the day of the outbreak, the pool water had been dyed for a Halloween-themed party in the early evening.

Chlorine levels are knowingly lowered when the dye is added to the water, but remains within national pool water advisory guidelines, to allow the dye to take effect.

Responding to the report, Medway Council said: "Staff have good experience in using the colouring dye and manufacturer’s guidance is always followed. The product has been used at more than 10 special pool events since 2015.

"The normal operating procedure for Medway Council-run swimming pools includes a high but safe amount of chlorine - twice the national minimum guidance amount.

"At the time it was quickly determined that norovirus was the cause of the illness, and the pool and changing areas underwent an urgent deep clean as soon as reports of illness were received.

"As a precaution going forward, the council will no longer use dye in its pools."

PHE concluded that "prompt and robust actions undertaken by leisure management and Medway Council’s environmental health team in response to the reported outbreak mitigated further risks to pool users".

Following their findings, PHE has suggested that a review of scientific evidence may be needed to determine how much chlorine is necessary to prevent the spread of norovirus in water. PHE is taking this up with the Pool Water Treatment Advisory Group advisory group (PWTAG), which publishes national guidance on pool water safety.

PHE has identified that strict compliance with Medway Council’s normal robust operation procedures would minimise the risk of further outbreaks occurring in the future. Also, that enhanced vigilance and oversight should be considered when deviating from normal pool procedures.

It has been recommended that staff undergo additional training on the need to maintain clear records after measuring chemical levels, and should also consider ways to improve the use of showers before and after pool use by customers – the council says they have already addressed both points.

Medway Council’s Portfolio Holder for Community Services Cllr Howard Doe said: “We have worked closely with Public Health England to look into how customers could have become ill after visiting Splashes. I would like to say again on behalf of the council that we are sorry to those who felt unwell after enjoying the pool party.

“This was a rare and isolated incident for Medway. We have a fantastic range of leisure facilities in Medway, all of which are run in-line with strict health and safety guidelines to ensure residents and visitors have an enjoyable experience.”