Aucklanders have failed to save enough water for a second day running.

Watercare says the 409 million litres used yesterday across the region was still above the vital 400m litre limit, even though it was 10m less than Monday.

Watercare said it was doing everything possible to avoid a boil water notice, including increasing capacity at all treatment plants.

"Auckland has demonstrated that we can reduce our water consumption without significant inconvenience. But as the weather improves and the weekend's storms become a distant memory, we run the risk of forgetting the need to reduce water use," said Watercare chief executive Raveen Jaduram.

"The reality is we are still dealing with 100 times more silt at our Ardmore treatment plant. And so we need to remember every day to reduce our water use by 20 litres per person."

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He asked people to avoid washing cars and turn off auto-irrigation systems.

Watercare also praised efforts by commercial customers for water savings including petrol stations that had temporarily switched of car washes.

"We welcome Z and Caltex closing their commercial car washes across Auckland in an effort to reduce water use and encourage other businesses to follow their lead," said Jaduram.

Yesterday Auckland University was found defying the water savings by running sprinklers over the weekend.

Auckland Council's development arm Panuku also ran sprinklers in Wynyard Quarter on Saturday.

On Friday, Watercare urged the public to stop watering gardens, washing their cars and to have shorter showers after storm damage to the Ardmore treatment plant meant it was treating 50 per cent less water than usual.

The council now has all sprinklers and fountains switched off and Auckland Transport has also ordered that waterblasting at its bus shelters, train stations and platforms only be done if absolutely necessary.

Initially the region met the savings target but since the start of the working week has failed on consecutive days.