The South Wairarapa District Council says it hasn't been able to fully flush Martinborough's water network, and a boil water notice remains in place in the town.
E coli was detected in the town's water supply late last month.
The network was meant to be completely flushed with fresh water overnight - the final step to making the water safe to drink again.
The council said the flush had to be stopped before it could be completed, because there was an issue with not being able to maintain enough pressure to supply water to all houses.
Another flush is being planned for Sunday night.
Some houses lost water, but it should be back on for everyone now, the council said.