One-time America's Cup yachting commentator Penny Whiting says yachties can teach other Aucklanders a few tricks to save water.

Whiting, who runs the Penny Whiting Sailing School, says she is now soaping herself before turning on the shower, brushing her teeth in a cup, and measuring one cup of water into a kettle if she is making tea for one at home - just as she has done for years at sea.

She and other Aucklanders have cut the region's water usage from a usual March average of 450 million litres to an average of 404 million litres a day this week, easing the risk that partially treated water will have to be piped into homes after last week's heavy rain.

"We yachties are very economical with water, it's a precious commodity on a boat," Whiting said.

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"When you have a shower you step in, wet yourself, turn it off, then shampoo, using half as much shampoo as you normally would, and then turn the water on.

"Whoever is on board has their own cup with their initials on, and when you brush your teeth you half-fill it with water, you dip your brush in and clean your teeth. The trick is don't use too much toothpaste.

"I'm also obviously only showering every second day."

Watercare said yesterday that the water savings, plus a gradual recovery of the Ardmore treatment plant, had reduced the chances that it would need to feed partially treated water into the system, which would trigger a call to boil drinking water.

Water supply manager Priyan Perera said Ardmore's output was initially almost halved from 330 million to 175 million litres a day because the amount of silt in the water hit about three times its level of the last big rainfall event, Cyclone Wilma in 2011 - "outside the envelope" that the plant was designed for.

He said the water treatment process involved collecting solid particles together so that they could be removed.

"You have to adapt the plant operating system to deal with that increase in particles coming at you," he said.

"We are now gradually increasing production by 5 million litres a day, but we are not sure if there is going to be a limitation on that."

Perera said his own neighbours had responded to the call to cut water usage.

"One guy wanted to wash his car last week and said, 'No, I'm going to leave it, you let me know when I can,'" he said.

"I know some who have bought hourglass-type timers for the shower, particularly for kids so they're not too long in the shower."

Big water users trimming down

Auckland International Airport said it had cut water use in the airport precinct by 180,000 litres a day (9 per cent). It has stopped washing its emergency vehicles and refused a request for fire engines to provide a "water arch" for an aircraft to mark a pilot's retirement.

The University of Auckland and Auckland Council said they had stopped washing windows and buildings and turned off sprinklers and fountains. Lion Breweries said it cut output at its East Tamaki plant by 40 per cent this week for maintenance.

DB Breweries said it also reduced water usage, but without cutting output.

Langham Hotel sales manager Michael Shah said guests had been asked to take "short showers" rather than baths.
Z Energy, Caltex and Mobil have closed their car washes.