The characteristics capable of supporting Type 1 pits were determined empirically by Lucey after examining the compositions of waters in which the pitting behaviour was known. They should be cold, less than 30°C, hard or moderately hard, 170 to 300 mg/L carbonate hardness, and organically pure. Organically pure waters usually originate from deep wells, or boreholes. Surface waters from rivers or lakes contain naturally occurring organic compounds that inhibit the formation of Type 1 pits, unless a deflocculation treatment has been carried out that removes organic material. Type 1 pitting is relatively uncommon in North America and this may be a result of the lower population density allowing a significant proportion of the potable water to be obtained from surface derived sources. In addition to being cold hard and organically pure, the water needs a specific chemistry. The effect of the water chemistry can be empirically determined though use of the Pitting Propensity Rating (PPR) a number that takes into account the sulfate, chloride, nitrate and sodium ion concentrations of the water as well as its acidity or pH. A water with a positive PPR has been shown to be capable of propagating Type 1 pits.