These tanks can be constructed of concrete blocks. The tanks are partly (1.5 m) built below the soil surface. These tanks can store up to 20,000 liters of water, used for domestic use, cultivation.
With regard to the concrete block tanks, 40 community water tanks (supporting a few families each) were implemented successfully. Following this success, another 80 concrete block tanks will be built at household level.
Practica foundation is testing various options for low-cost storage and groundwater recharge like the "Reed cement tank" and the "Tube recharge".
==Field experiences==
* The Brazilian government, with support from organisations such as UNICEF and IRCSA (International Rainwater Catchment Systems Association) started a programme to construct one million rainwater tanks in Brazil. With regard to the concrete block tanks, 40 community water tanks (supporting a few families each) were implemented successfully. Following this success, another 80 concrete block tanks will be built at household level.
* In China, clay has been used to line excavated water cellars (called Shuijiao) in areas where the natural soil (loess) is already fairly impermeable. The lining process is difficult and time-consuming and has been replaced largely by ferrocement or plastic. However, it proves that in some areas it is possible to construct a low-cost tank.
* In Somaliland, similar water cellars were observed that were excavated in impermeable stable soil formations – runoff water entered through a small inlet channel. Other tanks are sealed with a 10cm unreinforced cement lining – it seems that 30m3 is the most economical size as the most volume had that doesn't need reinforcement – such tanks cost US$189 or about US$6.3 per m3 of storage (materials only, presumably).