No washing clothes, no turning on the dishwasher ... and flush number twos only

Oamaru residents are being told to use water only when absolutely necessary for the next four days.

The town's water system has been affected by this week's torrential rain and the Waitaki District Council says they need to seriously reduce water usage for the next four days to let things recover.

If that doesn't happen, it warns it may run out of treated water, which would means schools and businesses could have to close.

Residents in the Timaru district are also facing water restrictions after the rain stirred up mud in the Pareora River, meaning the reservoir can't be replenished until it settles down.