Scottish Water said customers in Shawlands, Pollokshields, Mount Florida and Newlands were affected.
Roads, including the Jamaica Street Bridge, were closed while the burst was dealt with last night.
A spokeswoman for NHS Greater Glasgow and Clyde said: "Some wards in the old hospital are without water, but bottled water is being brought in.
"Patient care has not been affected."
A statement by Scottish Water said: "A squad will be on site shortly to carry out the necessary repairs and will restore supplies as soon as possible."