The 'our water use' section of the council website shows 173,354,000 litres of water were used in the city on Sunday.
That is an average of 307 litres per person and is a 25 per cent reduction from the same time last week.
Beaumont said the system can manage when the water usage doubles in the afternoon - which is the busiest period of the day. But, on hot days demand can exceed those peaks, and the network starts to struggle.
"What can happen in the afternoons on those hot summer days, is that the demand can double again, it's four times - and sometimes five times that peak hourly demand - when the day gets very hot, and that's when we struggle to get enough waters to our reservoirs and maintain those pressures in the network.
When reservoirs and water pressure are affected, it can create problems if steady supplies of water is needed for activities like firefighting.
To keep water use low, the council has published a series of tips to reduce water use around the home, including watering the garden in the morning when it's cooler, turning the tap off when brushing teeth, and washing only full loads of clothes.