Understanding 'Detected,' 'Median,' and 'Range' in Washtenaw County pH Sampling
'Detected' Means Measured Value Recorded
In the US Geological Survey data for Washtenaw County aquifer 112SDGV, pH was measured in 13 samples from 5 wells. 'Detected' means a pH reading was recorded each time; no samples fell below the reporting limit. Detection only confirms the presence of a pH reading, not a problem.
'Median' Represents the Middle pH Value Among Samples
The median pH in this area was 7.4 standard units, which indicates that half the samples had pH above and half below this point. The median gives a central tendency but does not describe extremes.
'Range' Shows the Spread of pH Values Measured
The range was from 7.1 to 8.0 standard units. This range indicates how much pH varied across the wells sampled but does not indicate any readings below 6.5, the lower secondary EPA standard for pH.
What Happens When Acidic Water Is Not Addressed Over Time
Material Effects on Plumbing and Fixtures
Consistent exposure to water with a low pH can contribute to accelerated wear on plumbing materials such as metal pipes due to mild corrosivity, potentially leading to aesthetic issues like staining or metallic taste. However, the area's measured pH values do not indicate such acidic conditions based on government sampling.
Potential Appliance Impact
Acidic water may reduce the lifespan of appliances that use water, including water heaters, by increasing mineral dissolution or corrosion. This effect depends on the specific pH of household water, which requires testing.
Reading the Record: Practical Example for Washtenaw County Homeowners
Using Median and Range to Gauge Expected pH
The median pH of 7.4 standard units and range from 7.1 to 8.0 suggest that typical water in this aquifer is neutral to mildly alkaline. Since all recorded values are above the EPA’s secondary lower limit of 6.5, homeowners probably experience water that is not acidic.
Why Your Water Could Differ
Your well's pH can only be established by direct testing. Local aquifer conditions are informative but do not guarantee your well's result.
How Acidic Water Differs From Commonly Confused Issues
pH Versus Hardness or Iron Content
Acidic water relates to pH, which measures acidity or alkalinity. This is distinct from water hardness (minerals like calcium and magnesium) or iron content, which have different treatment approaches and effects.
Corrosivity Versus Safety Standards
The EPA’s pH standard in this case is secondary, aimed at aesthetics and material compatibility, not health risk. Acidic water does not imply unsafe water unless other contaminants are present.
Seasonal and Multi-Year Variations in pH from Sampling Dates
Data from 2016 to 2024 Indicates Stability
The sampling dates spanning over nearly eight years show pH consistently within the 7.1 to 8.0 range. This suggests stable water conditions in the aquifer over time without significant trend toward acidity.
Variation Across Different Wells Sampled
Sampling from wells ranging 49 to 145 feet deep shows consistency across depths, indicating minimal variation in pH due to well depth in this aquifer.
Differences Between Public-System Records and Private-Well Testing
Public Record Reflects Area Trends, Not Individual Wells
The USGS data represents multiple wells across Washtenaw County aquifer 112SDGV, not individual household wells. Local well testing is required to confirm specific water quality at your home.
Private Testing Essential for Treatment Decision
Because individual well water can differ from area samples, private testing is the only way to determine if your water is acidic enough to require treatment.
Summary
Deciding how to address acidic water involves understanding local pH sampling data and recognizing that area trends cannot substitute for testing your own well. The USGS data for Washtenaw County aquifer 112SDGV shows pH levels consistently within the EPA’s secondary standard range, suggesting typical water is not acidic.
If private testing shows acidic water, the Autotrol Acidic / Low-pH Water Filter ships ready to configure as a documented solution for adjusting pH and protecting household plumbing and appliances.
Where this information comes from
Source: USGS groundwater sampling. Sampled 2024-06-25. These figures describe groundwater sampled in this area. They are not a test of any individual private well - only a test of that well can establish its own water.
On record: U.S. Geological Survey sampling of pH in the 112SDGV aquifer (Washtenaw County): 13 results from 5 wells, median 7.4 standard units, range 7.1-8.0 standard units; EPA secondary standard for pH is 6.5-8.5 (aesthetic/corrosivity, not health-based); 0 of 13 sampled results fell below 6.5
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