Water quality of Piner Creek is characterized by pH levels that are mildly basic, with upper reach pH levels about 8.5, declining to lower reach levels at 7.8 just above the discharge to Santa Rosa Creek. The headwaters soils are typically of pH about 6.9.
The water quality of Piner Creek can be described as having a slightly alkaline character, with varying pH levels across different sections, from about 8.5 in the upper reaches to 7.8 near its connection with Santa Rosa Creek. The soil pH in the headwaters is typically around 6.9.