The $6.5 million Hyde Park fountain, opened inby Queen Elizabeth II a month ago, was July 22 after three people, including a child, slipped and injured themselves while wading in it.
Officials, who have already roughened the stone to prevent slippage, will monitor the fountain for a week before the public is allowed to visit again from Aug. 20.
A few tourists watched the water being switched on Thursday from behind a fence. Royal Parks said that fence will remain in place and the site will be tightly controlled with a limited number of people being able to enter.
Visitors will also be allowed only to dip their feet in the fountain from the edge, rather than paddle and play in the water as initially anticipated by its designer, American Kathryn Gustafson.