68e07683_SAHRA___Home_Water_Testing__Likely_source
[Lab result] Alkalinity high (pH levels over 8.5) [Potential health effects] Health effects minimal except for dry skin. Some studies indicate slightly alkaline water is better for human health than is water that is acidic. [Treatment options] Addition of acid chemicals or reverse osmosis or distillation systems (POE or POU) [Likely source] 
Naturally occurring alkalis in the soil and ground and surface waters
SAHRA - Home Water Testing
Likely source