A hole which appeared on the A23 closed the northbound carriageway between the Fleming Way and Lowfield Heath roundabouts yesterday afternoon (Sunday April 6).
A spokeswoman for Thames Water said the stretch was expected to remain closed until at least next week.
The hole was caused by a leak on a large pressurised pipe between Crawley and Gatwick Airport.
She said: “The A23 will be closed northbound between the Fleming Way and Lowfield Heath roundabouts.
“Thames Water is working with West Sussex County Council and emergency services to put diversions in place.
“The closure is expected to last beyond this week while investigations continue.
“We are sorry for any inconvenience this may cause and will open the road as soon as it is safe to do so.”
A spokesman for West Sussex County Council said the council understood the situation was “awkward” for Thames Water because the pipe, which transports sewage, will not be shut during its reparations.
He said a tanker would pump out the sewage as part of the works.