**Abstract**

Heavy metals, such as cadmium (Cd), arsenic (As), lead (Pb), and mercury (Hg), are often detected in water, causing detrimental effects to human health. This study assessed Cd, As, Pb, and Hg concentrations in drinking water from the greater Gaborone water distribution system supply area. The Inductively Coupled Plasma—Mass spectrometry was used to analyze 200 water samples from water treatment reservoirs, the distribution line, households, and bottled water. Heavy metal pollution was calculated using the heavy metal pollution index (HPI). Average heavy metal concentrations were in the order of Pb > Hg > As > Cd in the overall study, with lead exceeding the permissible limit set by the United States Environmental Protection Agency (US-EPA) in all the samples. Average lead concentrations from indoor taps were 15 times more than untreated raw water. HPI values were respectively 33.2 and 0.74 for the World Health Organization (WHO) and Botswana Bureau of Standards (BOBS). An increase in heavy metal concentrations post-water treatment suggests inadequate system maintenance and possible contamination of water during the distribution system from copper and lead soldered pipes. Further research on the treatment infrastructure and plumbing activities is suggested.

**Keywords:** drinking water, bottled water, lead, heavy metal leaching, Botswana, public health
