The 24-hour battle to prevent Kenley's water works from flooding and threatening water supply to 47,000 homes is a 'touch and go' situation.
Firefighters have been pumping 5,000 litres of water from the works - owned by Sutton and East Surrey Water (SESW) - every minute since 9pm yesterday when it was declared a 'major incident' by Croydon Council.
The pipes have transferred the excess flood water 800 metres down the road towards Kenley Primary Harris Academy school where children were sent home at midday.
Richard Rap, the site's operation's manager said: "It's touch and go at the moment with each new downpour adding to the possibility of the site being overwhelmed with flood water."
The Kenley water works provide water to 47,000 homes, but SESW spokesman said this evening there was "no immediate risk" to their water supply even if the works had to be shut down.
He said: "We are currently implementing our normal operational procedures preparing to re-route supplies from other sources should it be necessary.
"We also have treated water storage reservoirs in the area which will maintain supplies for several days and which will mean that there is no automatic loss of supply even if we are unable to produce treated water from our Kenley site."
Mike Van Der Vord, the Kenley and District Residents Association's (KENDRA) environment representative said the situation could worsen over the next few days.
He said: "The river Bourne is flooded in the area but it's source is up near Warlingham.
"If often takes two to three days for the deluge of water to travel down and make its full effect in Kenley; that's what most people don't realise."
The London Fire Brigade has been using a high volume pump, capable of pumping 300,000 litres of water an hour.
Representatives from the water company, the Environment Agency and Croydon Council have also been working at the scene and are likely to stay there all weekend as more rain is forecast.
Fire Commissioner Ron Dobson said: "Firefighters have been working very hard throughout the night to pump water away from the facility and protect it from flooding.
"The water works supplies tens of thousands of homes in the area so our crews are working extremely hard to bring this incident to a quick and safe conclusion."
The council has sent letters to around 1,500 homes and businesses that will potentially be affected if the water levels rise any further.
Although the basements of some properties have flooded, no homes have yet been told to evacuate because of the rising water levels.
The council is currently monitoring the river Bourne and officers have been clearing culverts, screens and road gullies.
Mr Van Der Vord said: "The field by Valley View Gardens is completely flooded.
"It used to be allotments until the flood in 2001 when the water became contaminated and it is now designed as a flood plain.
"The council have said it is currently 6ft deep and you can see birds sitting about on the top of it.
"In the face of it, they are doing the best they can."
