Some of the bases that are commonly available in the house include baking soda and ash. However, it is possible to get acidic materials including lemon juice and sulfuric acid. Sulfuric acid is commonly found in batteries.
Water will always have a pH. pH is a measure of how acidic or basic a solution is. Intruduction of basic substances such as carbonates will raise pH. Introduction of acidic substances such as carbonic or sulfuric acid will lower pH.