|Carpentry for Vocational Schools - A Teachers Handbook|
Tanks must be placed on a very solid, even and levelled surface in order to prevent them from cracking caused by uneven foundations.
a) Foundations for overhead tanks:
- An iron or timber frame is made to fit exactly to the slope or the ridge of the house. The frame must be braced correctly. Joists are laid and covered across with roofing iron. Roofing iron has the advantage of keeping the bottom of the tank dry because the rainwater will run off in the valleys.
Make the roofing iron longer than the frame to keep the construction dry. The whole frame is secured by nailing or screwing down to a purlin.
b) Concrete foundation: - Concrete foundations are required where the tank is near ground level and usually associated with a pump, because the outlet will be too low to give pressure to all tapes in the house.
The foundation is a simple concrete slab with an outside foundation going into the ground about 300 mm.
The surface must be completely leveled and smoothed. When dry, put a layer of "Malthoid" (Bitumen foil) to prevent the bottom of the tank from being in immediate contact with the concrete.
c) Stump foundations:
- When tanks need to be elevated in order to get sufficient water pressure in your kitchen or toilet, you can make it with a stump foundation. Steel, wooden or concrete stumps can be used.
- You have to be careful that you set the stumps at such a height, that there is later enough space left to fit the tank between the gutter and the top of the foundation.
- Stumps must be going at least 500 mm into solid ground and are surrounded firmly by concrete.
- Bearers must be 6"x2" (150 mm x 50 mm) and joists 4"x2" (100 mm x 50 mm) being placed upright ontop of the bearers with a spacing of about 150 mm. Roofing iron is nailed across. It must not be joined, to prevent water from entering to the joists and rotting them.