Water from a burst water pipe on Thursday afternoon caused flooding, leading police to warn drivers and residents to avoid the Tide Mill and Eling Toll Bridge area in Totton.
The water firm said after problems were found at the Testwood water treatment site its teams had worked through the night with the site producing water again early this morning.
It said it was working normally and customers in Southampton, Eastleigh, Romsey, Totton, Hythe, the Waterside and the New Forest remained in supply.
It added: “As a precaution, we began bottled water deliveries overnight to customers registered on our priority services register in some areas.
“These deliveries will continue throughout today to ensure support is available should it be needed.”