One of the largest projects in the history of Halifax Water begins tonight, and residents are being warned to conserve water or face a boil order.

Halifax Water will begin the work replacing the Pockwock water transmission main in Kearney Lake Road at 9 p.m. Friday evening. As a result of the work the portion of Kearney Lake Road near the transmission line that runs from the Pockwock Lake reservoir will be closed to traffic beginning at 6 p.m.

The plan is to replace the existing 1.7 kilometres of pipe that runs along the road at a total cost of about $11 million.

Crews will work through the night.

James Campbell, spokesperson for the Halifax Water Commission, said the work is expected to take about 24 hours.

He said the utility has enough water to last customers about 24 hours, but if the project runs long or if residents use too much, many of the homes which rely on the Pockwock supply will be forced to boil their water.

"We’re asking all Halifax Water customers on both sides of the bridge … to reduce their water consumption as much as they possibly can," said Campbell.

The plan is to replace the existing 1.7 kilometres of pipe that runs along the road at a total cost of about $11 million. (CBC)

"We’re not asking you to stop using water, we’re not asking you to stockpile water, there’s no need of that, there will be water. We’re just asking all Halifax Water customers to reduce as much as they possibly can … so we can complete our tie-in project and get the water system back in full operation."

Residents are advised to:

Avoid doing laundry

Avoid watering the lawn

Avoid washing your vehicle

Avoid filling pools

Campbell said it will be "business as usual on Monday," and hopes that the project goes smoothly, without delays.

The Pockwock water supply serves customers in Halifax, Bedford, Sackville, Fall River, Waverley and Timberlea.

CBC News will be following this story all weekend long. Follow us on Twitter @CBCNS for the most up to date information.