Water is the most common cleaning solvent for manufacturing processes. Water purity determines the quality of the final product. However, selecting the appropriate water for the application may not be readily apparent.

TAP WATER
Too many manufacturing cleaning operations use tap water. It is important to keep in mind that the requirements and goals of municipalities and manufacturers differ. Community health is the primary driver of drinking water specifications. Manufacturers need to acquire desired surface qualities. Tap water must comply with the EPA National Primary Drinking Water Regulations (NPDWR). Municipalities may add further requirements.

Drinking water may contain solid, organic, and dissolved substances that can interfere with industrial processes. Most localities purposefully add chlorine or chloramines as disinfectants; some add fluorides. The quality of water can vary greatly from location to location, and seasonally in a given location. This lack of control and consistency makes tap water undesirable for industrial applications.

ION CONTENT
One measure of ion content is electrical conductivity. The highest purity water has a conductivity of 0.055 micro-Siemens per centimeter, (S/cm). For low conduc-tivities (<1 S/cm), the common unit is the resistivity, the reciprocal of conductivity. Pure water is often referred to as 18 Megohm water (the reciprocal of 0.055 S/cm is 18 M-cm). Drinkable tap water can be up to four orders of magnitude more conductive.