Until then, residents along the entire Windward O'ahu coast are being asked to conserve water. Motorists were being advised to avoid driving through the area today.

"It's a mess," said Denise DeCosta, spokeswoman for the Honolulu Board of Water Supply.

First, the water main broke about 2:45 p.m. yesterday, prompting police to close Kamehameha Highway in both directions.

One lane of traffic was open to contra-flow traffic at 6:45 p.m. but work crews closed the highway at 10 p.m. so they could dig a trench around the pipe.

Then they noticed a large kamani tree looming over the break. A tree trimmer was called but he couldn't work until Hawaiian Electric Co. shut off power to lines mingled in the higher branches, DeCosta said.

At 1 a.m., the tree trimmers finally began a 5-hour job of digging out the tree.

By 8 a.m., water officials estimated there was still another 12 hours of repair work ahead and then another six to eight hours needed to fill pipes and lines that lost all their water, DeCosta said.

Ka'a'awa Elementary School was closed today because it had no water service.

Only 25 customers were directly affected by the break. They are getting their water from a water wagon.

"That is the best we can do right now," DeCosta said. "The people of Punalu'u are very patient. It has been a long haul and we are grateful to them. I am sure it is frustrating."

At nearby Countryside Cabins, business manager Chas Wagner said the vacation guests in his eight cabins were fairly upbeat about the lack of water for showers, teethbrushing and toilets.

"It was a little bit of an inconvenience this morning," he said. "We had to go to the 7-Eleven to get bottled water for coffee. It is sort of a mini adventure."

That view might not be shared by his maintance worker. He had to empty the hot water tanks so he could use the water to flush full toilets, Wagner said.

"You gotta do what you gotta do," Wagner said.

The rupture occurred in an area where installation of a new 30-inch transmission main is under way, a backup for the line that burst. A 12-inch main also runs parallel to the 30-inch line, and both lines were shut down.

The cause of the break was being investigated. DeCosta said officials believe that construction yesterday in the same area contributed to the break, in part because a lot of pipe was exposed.

When the break occurred, water service in the area was immediately affected. "It drained the Kahana reservoir," DeCosta said. "The reservoir was at 22 feet when the pipe broke. Within a very short time it went down to 4 feet. So a lot of water was lost."