I have a problem with progressive encrustation or scaling of CaCO3 within a distribution system in an underdeveloped area in central Africa. The raw water source is a relatively warm (~70 deg F, ~21°C), from a volcanic lake that is alkaline and highly mineralized. Raw water pH is about 11 and raw and finished water LSIs are about 1.3. There is no centralised treatment. The only treatment is coarse screening at each raw water pump station and the addition of calcium hypochlorite for disinfection. Mixing and dosage of calcium hypochlorite are poorly controlled. Can calcium from the calcium hypochlorite be binding with carbonates and bicarbonates from the lake water? LSIs for both raw and finished water are high. How significant of a role does the CaCO3 play in scaling? One option to consider is to switch to sodium hypochlorite. Could this solve the scaling problem? Given the lack of centralised treatment and supply chain issue, pH treatment is not possible in the near future.