Sutton and East Surrey Water is reassuring its customers the water treatment works at Kenley is operating normally – despite the flooding emergency currently taking place in the valley.
The company is carrying out additional tests to ensure water quality is being maintained.
But the managing director Anthony Ferrar said this is just a precaution.
He said: “We have no concerns about the quality of the water leaving the works.”
More than 46,000 properties and 116,000 people receive their water from the works.
If it does have to shut down the company says it is planning to supply customers by re-routing additional supplies from other treatment works.
The company is working closely with Croydon Council, the London Fire Brigade, and other agencies to ensure flood defence work and efforts to remove the water are coordinated as the inundation is affecting a wide area and homes are threatened with flooding.
Mayor of London Boris Johnson visited the treatment works in Godstone Road on Tuesday and praised the response to the flooding at the works and surrounding area, calling it an ‘extraordinary operation’.
His visit came a day after the Secretary of State for Communities and Local Government Eric Pickles visited the site and expressed similar admiration for the flood defensive work and related activities.
Mr Ferrar added: “There is always a concern that rumour and misunderstanding may occur in a sometimes fast changing and developing situation such as this involving multi-agency and contractor support.
“I would strongly advise all of our customers to check any information or advice they may receive about their water supply directly with us.
“We are providing continuous updates and additional information on our website at waterplc.com or telephone customer services on 01737 772000.”
Customers can also email the company at WaterSupplyEnquiries@waterplc.com