The Water and Sewerage Authority (WASA) said it may take another 24 to 72 hours for the water supply to normalise to some affected areas.
The water supply and other public utilities were affected by a power blackout on Wednesday afternoon.
In a media statement on Thursday morning, WASA said operations started at 8 am on Thursday, at its water treatment plants and production wells, except for the Aripo and North Coast facilities, were being worked on currently.
WASA said booster stations were also offline, to allow the transmission pipeline systems to continue to recharge, which will allow for the systematic restart of the facilities.
It added that the Point Lisas and Point Fortin desalination plants, owned and operated by Desalcott and Seven Seas Water, also restarted, and were in the process of ramping up operations towards full production by Thursday afternoon.
According to TTEC’s general manager Kelvin Ramsook, Wednesday's blackout was due to a fault which developed in one of the major circuits which triggered their independent stations to shut down.