(e)Water supply shall be provided to give flow of water as required under clause (a) for at least 100 minutes. At least 50 per cent of this water-supply for 4,50,000 litres whichever is less, shall be in the form of static tanks of adequate capacities (not less than 4,50,000 litres each) distributed round the factory with due regard to the potential fire risk in the factory (which piped supply is provided, the size of the main shall not be less than 15 centimeters diameter and it shall be supplying a minimum of 4,500 litres per minute at a pressure of not less than 7 kilograms per square centimeter.