Because of yesterday's flash flooding, the Ardmore Water Treatment Plant was treating about 50 per cent less water than usual.
That was because much of the water now contained a lot of silt from slips - giving the water a muddy hue and therefore making it more difficult to treat.
It would take up until the end of the month before silt would settle in the dams, he said.
Auckland was not reliant on a single water treatment plant, with five treatment plants in place for the city's water treatment.
They included one in Waikato and another in Huia, which were both running at full capacity.
"Our focus is on ensuring our customers receive high-quality water that is safe to drink straight from the tap. We're achieving this at the moment.
"But we have had to cut back on the volume of water being treated at our largest plant in order to maintain this quality,'' Jaduram said.
"I would like to emphasise that we're not enforcing water restrictions - we're simply calling for voluntary savings following an extraordinary and unprecedented weather event in the Hunuas.''
WAYS YOU CAN SAVE WATER -
• Cut your shower time by two minutes. Approx saving = 16L
• Turn off the tap when brushing your teeth. Approx saving = 4L
• Don't use your toilet to flush rubbish. Approx saving = 7L
• Only run your dishwasher when full
• Only run washing machine when full