How hard is the water in Monmouth County, NJ?
3.2 grains per gallon
You do not need a softener here.
The median hardness measured in Monmouth County, NJ is 54 mg/L as calcium carbonate, which is 3.2 gpg. That is soft on the USGS scale. It comes from 141 samples at 60 sites between 1990 and 2023, drawn from groundwater wells, which is what most taps and private wells in the county draw on.
How much it varies here
Half the sites came in between 1.5 and 5.1 gpg. That spread crosses a decision line, so some homes here land on a different answer. A $10 test strip on your own tap settles it. Confidence in the county figure: high (how it is measured).
What to do next
You can skip the softener. At 3.2 gpg the most a softener would fix is the odd water spot. If a salesperson in Monmouth County says otherwise, ask to see their reading in grains per gallon and compare it with this one. Because Monmouth County straddles a decision line, check your own tap with a $10 test strip before you spend anything.
More on when a softener is not worth it.
From 0.4 to 289.2 gpg
The softest single sample on record in Monmouth County was 6 mg/L and the hardest 4,950 mg/L, an 825-fold gap. The top quarter of sites read above 5.1 gpg and the bottom quarter below 1.5 gpg. So even in a soft county, a handful of wells here produce water hard enough to scale a heater.
Wells 3.2 gpg, rivers and lakes 3.1 gpg
141 groundwater samples from 60 wells put the median at 54.3 mg/L. 888 surface samples from 59 sites put it at 53.9 mg/L. In Monmouth County the wells come out 0.1 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. The two sources are close, so the county figure should hold whichever one your tap is on.
Monmouth County against the rest of New Jersey
Among the 21 New Jersey counties with data, Monmouth County is number 14 of 21 counting from the hardest. Across the whole country it is harder than 22% of counties.
Softest in New Jersey: Ocean County at 0.8 gpg. Hardest: Hudson County at 17.2 gpg. Closest to Monmouth County: Cape May County (2.8), Cumberland County (2.5), Burlington County (2.4).