Aucklanders have beaten the target of using less than 400 million litres of water by 10 million litres.
Watercare has asked people to cut water use by 20 litres, or one-eighth of the current average of 160 litres per person per day, until sediment in the waterlogged Hunua Ranges drops enough to stop clogging the water treatment plants.
TodayWatercare announced those in the Auckland region were doing a "fantastic job" of conserving water.
Chief executive Raveen Jaduram commended Aucklanders for their efforts but said the city is not out of the woods yet.
"It's really inspiring to see the community responding so well to our call for reduced water use," Jaduram said.
"I would like to thank everyone in Auckland for your effort to date. You're doing a fantastic job.
"The situation at our Ardmore Water Treatment Plant remains serious and we do not expect that to change in the next few days. Therefore, the challenge for Aucklanders is to continue to use less water, especially when the weather improves later in the week.
"Our Save 20 target is easily achievable: 20 litres less water per person per day. To put it in perspective, it's only a few minutes less in the shower and turning off the tap when brushing teeth. Together, we can all do this."
Watercare's treatment plants are producing enough water to meet demand and the quality of the water has not been compromised. It's safe to drink straight from the tap.
However, if the demand for water goes up substantially, the company may be forced to release partially treated water into the region's supply.
In such a situation, a boil water notice would be issued.
"The clarity of the water entering the Ardmore Water Treatment Plant is still about 100 times worse than what we would expect to see entering the plant," Jaduram said.
"This is because there were significant slips and erosion in the Hunua Ranges, where Auckland's largest water storage dams are located."
The Save 20 message applies to everyone connected to Auckland's metropolitan water supply network, including those living as far south as Pukekohe and as far north as Waiwera.
MetService has advised that a small low will cross over Auckland about midday today, accompanied by potentially damaging winds, a chance of tornadoes and another burst of heavy rain. A severe thunderstorm watch is in place between 8am to 2pm.
The worst of the wind and rain should occur around noon or in the early afternoon. Localised gusts of 100-120 km/h are possible, particularly around Great Barrier Island. This is a fast moving and very unstable system with a risk of small tornadoes anywhere across the region.
Winds should ease after 2pm and remaining showers should start to clear.
How to reduce your water use:
1. Cut your shower time by two minutes: Saving = 16 litres
2. Turn off the tap when brushing your teeth. Saving = 4 litres
3. Only run your dishwasher when it's full.
4. Only run your washing machine when it's full.
5. Use the half-flush on your toilet.