Repairs to a burst water main, which closed a main road in Rickmansworth, are expected to last until this evening.
Uxbridge Road in Rickmansworth has been flooded by a burst pipe. The A412 is closed between Denham Way and Grove Road.
Traffic is building back down to the BP garage, with long tailbacks in Church Lane and the town.
Kevin Barton, an Affinity Water spokesman, said: “We would like to apologise for any inconvenience caused by a 10” burst water main on Uxbridge Road.
“The burst was reported to us at 12.45pm and Affinity Water engineers arrived at 1.30pm to shut down the main and begin repairs.
“No customers were affected by this burst and it is expected that repairs will be complete this evening.
“We would like to thank customers for their patience whilst we carry out these repairs.”