San Leandro Water Hardness & Quality Report (2026)

The East Bay Municipal Utility District (EBMUD) supplies water to San Leandro and 21 other East Bay communities across Alameda and Contra Costa counties, serving more than 1.2 million people. The primary source is the Mokelumne River watershed in the Sierra Nevada foothills. Water is impounded at Pardee Reservoir, constructed in the early 1920s, and transported via three 6-foot-wide steel aqueducts across the Central Valley to Walnut Creek — a distance of more than 80 miles. Gravity alone can move up to 202 million gallons per day, with secondary storage reservoirs holding enough supply for four to six months.

The Mokelumne River watershed drains the western Sierra Nevada, dominated by Precambrian and Mesozoic granitic and metamorphic bedrock. The granite terrain — composed primarily of quartz, feldspar, and mica — is naturally low in soluble minerals such as calcium and magnesium. These granitic rocks do not readily dissolve into flowing water, and the watershed's high elevation and rapid runoff further limit mineral accumulation, preserving the water's naturally soft character throughout its journey to treatment plants and distribution.

Soft water presents minimal scaling problems in household appliances, water heaters, and pipes; soap and detergents lather readily and mineral buildup is rare. Water softeners are not necessary for mineral control, and residents typically notice improved lathering and reduced spotting on dishes. A key concern with soft water is potential corrosivity — soft water can leach lead and copper from older plumbing if pH is not carefully managed. EBMUD adds chloramine and fluoride at treatment plants before distribution through more than 3,944 miles of pipes and 164 neighborhood reservoirs; lead levels are generally low, though the utility recommends testing if concerns arise.