Water supplies have been returning to the Skelmorlie, Wemyss Bay and Inverkip areas overnight.
Scottish Water has successfully completed repairs to the burst 18" strategic water main at Whinhill Primary School, Greenock.
The burst affected 12,000 homes yesterday including properties in Greenock and Gourock.
A Scottish Water spokesperson said: "We are now beginning to recharge and restore the water network to its normal set-up, however, due to the size of water main, this may take some time before full pressures are restored to customers.
"To support with this process, we will continue to tanker water into the network and assist customers where required until we have fully restored water supplies.
"As supplies begin to restore, some customers may experience discoloured water.
"If you experience brown water, we advise to allow your cold-water kitchen tap to run at a reduced pressure until this runs clear. Do not run any other taps or use any water appliances whilst doing so and follow the same process with any other taps affected once the water is clear from your cold-water kitchen tap.
"If you experience white water, this is air trapped in the supply and will clear within 24 to 48 hours.
"Our teams have worked throughout the night and early hours of the morning to carry out complex repairs to this strategic water main and we would like to apologise to all customers impacted and thank them for their patience and understanding."
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