The main burst on Wednesday afternoon outside of the Southern Water headquarters on Yeoman Road.
A Southern Water spokesperson said: “We have closed one lane of the roundabout at the junction of Palatine Road and Littlehampton Road (BN12 6JN) following a significant burst main on Wednesday.
“At present Westbound traffic will have to follow the diversion “Offington Lane >> A27 >> A280” and cannot pass the roundabout.
“Due to the burst’s proximity to an electrical cable and other services, we have to proceed with caution.
“We do understand this is frustrating for road users and local residents and would like to reassure those affected that our crews are working hard to fix this issue as quickly and safely as possible.
“We liaised with the council to ensure traffic management was in place while we carry out this vital repair and the road will reopen as soon as this work is complete.
“We’re working as quickly as possible to resolve this issue and apologise for any inconvenience caused.”
There is no estimated completion time yet and road users are encouraged to check for updates on Southern Water website and social media pages, the spokesperson said.
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