Scottish Water received reports from customers in the morning whose homes had suffered a loss of water supply or reduced water pressure. The agency said the problem had been caused by a faulty valve which feeds the south Glasgow and Renfrewshire areas.
The affected postcode areas included G41, G42, G53, G52, G41, PA1, PA2, PA3 and PA4. These cover Govan, Ibrox, Hillington, Cardonald, Bellahouston, Mosspark, Crookston, Pollok, Darnley, Paisley and Renfrew.
Supply has since been restored to most areas but Scottish Water said some higher properties may be experiencing low pressure.
A spokesman said: "We understand the frustration that this outage has caused for customers and apologise.
"Our Engineers are working hard to make sure the water network continues to refill. We expect to see normal service restored as soon as possible."