3.1 What are essential requirements for an effective storage tank? Name at least 3!
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Essential requirements for an effective storage tank are:
- a functional and watertight design with a solid and secure cover
- a screened inlet, overflow pipe and a covered manhole
- an extraction system which protects water quality, and a soakaway
- a maximum height of 2 m (unless additional reinforcement is used)
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3.2 Compare above ground and below ground storage. In which situation would you prefer below-ground storage?
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Below ground storage is indicated if
- runoff from the (soil) surface is to be collected
- large volumes have to be stored and the cost is essential: below ground tanks may have a cheaper cost per m³ stored water
- water quality is not really essential: below ground tanks may get easily contaminated from unwanted surface water runoff or groundwater
- emptying the tank is not a problem, because buckets or simple handpumps are available
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3.3 What is a frist flush device?
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Debris, dirt and dust will collect on the roof of a building or other catchment during periods without rain. The first rains carry this unwanted matter and would wash it into the tank if it were not diverted. The diversion of this first water is done by a first flush device
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3.4 What criteria would you use for guttering of the rainwater systems in Tamale?
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- factory made PVC
- factory made galvanised iron in different shapes
- self-made gutters from galvanized sheets (e.g. as V-shape)
- made of wooden boards or bamboo
What is the material used in the area? Are there already gutters at some of the houses? Made of which material? Can they be bought in stores? Or would it be cheaper to manufacture them yourself (e.g. as v-shaped galvanised iron)?
Important:
- sizing them correctly so that they carry all the water
- making sure that they carry all the water from the roof
- fitted with splash-guards if necessary to prevent overshooting (water running off the roof and not collected in the gutter)
- appropriate slope towards the storage tank (e.g. 1%)
- “straight” slope so that all water is drained and no standing water is left after the rains
