Tshwane metro emergency spokesperson Johan Pieterse said on Tuesday workers accidentally dislodged a 600mm pipe in the suburb Annlin.
This resulted in a substantial amount of water escaping from the reservoir and flooding an estimated 30 homes.
Emergency services were called in to ensure the water flowed away and that no further damage occurred.
Work would continue through the night to restore water supply.
The suburbs affected are Pretoria North, Annlin and parts of Sinoville.
The city would be providing tankers to the affected suburbs to ensure residents had drinking water, said Pieterse.
Full water supply was expected to be restored by Wednesday afternoon.