Can we have a reduction in price if we use water off peak?

Unfortunately not. If there is a low/high demand for water, it still costs the same to treat it and maintain the water supply. Water supply differs from energy where the customer demand for electricity means power stations need to increase output immediately at busy times to meet demand. Water is pumped and then supplied via local water towers and supply reservoirs; we optimise our pumping during the day to make sure that water is available locally for the peak demand times.