Scottish Water has warned of disruption to the water supplies to outlying parts of Aviemore and nearby Boat of Garten, Dulnain Bridge and Kincraig.
The company said emergency repairs would be carried out between 2100 BST on Tuesday and 0300 BST on Wednesday.
A leak has been found on the pipeline carrying water from Loch Einich high in the Cairngorms to treatment works at Blackpark, near Coylumbridge.
About 900 customers receive their water from the treatment plant.
Scottish Water said people who think they will need water after 2100 BST could store some in clean, covered containers in their fridge.
It said washing machines and dishwashers should not be used during the repairs.