Abstract: One hundred water samples were collected from the residential galvanized steel water storage tanks from three different regions of Al-Karak Province in the southern part of the country Jordan. Samples were analyzed for major anions (HCO3, F-, Cl-, NO3- and SO4-2), major cations (Na+, K+, Ca2+ and Mg2+) and heavy metals (Pb, Fe, Cu, Zn, Mn and Ni), in order to evaluate the impact of the residential storage tanks on the drinking water quality in comparison to its water source. The water quality of storage tanks showed higher ionic concentrations in comparison to its source. This was attributed to dust entering the storage tanks during the dusty summer season and the elevated water temperature leading to further evaporation from the tanks. Despite the fact that the contact period between the water and the residential storage water tanks is short (less than one week), elevated levels of heavy metals were found in the drinking water indicating dissolution of these metals from storage tanks to the water. This is enhanced due to the fact that many storage tanks were in wear and tear conditions and some not cleaned for a long period of time. Elevated levels of heavy metals in the drinking water from the residential storage tanks were noticeable in comparison to its source water; these levels were still below the Jordanian drinking water standards and didn`t exceed the World Health Organization standards for drinking water.