Spherical Watertank

Normally ferrocement water tanks are constructed with straight sides and rectangular of cubical in shape. A novel spherical shape has been constructed. The weight of concrete ( ferrocement mortar in this case) in this 6.4 mtr dia water tank is 16 tonnes and it holds water of about 1,20,000 ltr ( thus the concrete weight is only about 13 % of the weight of water. Refer Photo 22.

A sphere is a very exiting geometric form and its unique properties make it the most appropriate water tank. For a given volume, a sphere has a minimum surface area compared to any other form, i.e. more efficient use of construction materials. A sphere has no sharp edges or corners to lodge bacteria and dirt. The tank is very easy to clean.

Hoop tension due to water pressure is maximum at 0.6 depth ( from bottom) and it goes no decreasing to zero at the base of the tank. On the contrary a rectangular tank has maximum hoop tension at the bottom. In the case of underground tanks, the earth pressure provides uniform compression on the surface of tank to efficiently balance the hoop tension resulting from water pressure.

A spherical water tank in RCC or steel would be very costly due to excessive shuttering cost or sheet formation cost. No shuttering is required for ferrocement tank. Only temporary supporting is required during hardening of mortar.

All piping for supply , return and overflow and washout are placed within the tank.