A burst water main has affected around 36,000 properties in Renfrewshire and Inverclyde.
Scottish Water said customers may be experiencing loss of supply, low pressure or discoloured water.
The utility firm is currently working to repair the 24-inch strategic main close to the A726 in Erskine, which burst at around 12am on Thursday.
Affected areas include Erskine, Gockston, Shortroods, Ferguslie, Inchinnan, Bishopton, Port Glasgow, Greenock and Old Kilpatrick.
A Scottish Water spokesperson said: “Operatives have isolated the burst and are working to repair it, with water being both backfed from a neighbouring supply zone and tankered into the local network to enable the restoration of normal water supplies to properties as quickly as possible.
“When individual properties have their normal water supply restored will depend on their location on the water network.”
There has been localised flooding in the immediate vicinity of the burst, with the A726 currently closed between Barrholm Roundabout and the roundabout on the approach to the A898.
Diversions have been put in place and drivers are advised to leave some extra time for journeys.
Once supplies are restored, customers experiencing discoloured water should run the cold tap in their kitchen until it runs clear.
The Scottish Water spokesperson added: “We apologise for any inconvenience caused by this burst and thank affected customers for their patience and understanding while these emergency repairs are under way.”