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 exhibits a slightly alkaline profile, with higher pH levels observed in the upper sections (around 8.5) and lower levels just before it joins Santa Rosa Creek (about 7.8). The soil pH in the headwaters is generally around 6.9.