Thames Water has started up its desalination plant at Beckton in East London.
According to a report in the Daily Telegraph on Friday, the company said it was not a sign of any impending water shortages and that it was currently running the plant as a test.
The Thames Gateway Water Treatment Works, Britain's first desalination plant, is capable of supplying 150 million litres of water per day - enough to supply about one million people or 400,000 households. The works will take water from the tidal Thames when required and use desalination to remove the salt, producing high-quality drinking water.
Thames Water spokesman Simon Evans said:
"We began using the desalination plant at one-sixth output on March 30, not because we need to but as part of the fine-tuning of the works and the training of its operators, and we have been using it intermittently since then."