Patients at Watford General Hospital were given bottled drinking water yesterday after a problem was detected with the water supply.
An "internal incident" was declared at 2.15pm, and Watford firefighters reported that they were called in to assist after a water main "ruptured".
A spokesperson from West Hertfordshire Hospitals NHS Turst, said: "As you would expect, we have put in place a series of measures to ensure we continue to provide the best possible, safe care to our patients until the issue is resolved.
"This includes having the fire brigade on site to provide a temporary water supply, and we would like to thank them for their support.
"Basic non-drinking water supply has now been reinstated and we anticipate that the drinking water supply will be available later this evening. In the meantime, bottled water is being made available."