Allentown Water Is Very Hard — Here's What It Costs You Each Year

Why Is Allentown Water So Hard?

Allentown’s water measures 13 GPG (222.3 ppm), which puts it squarely in the “very hard” category. That’s nearly double the US national average of about 7.3 GPG, according to USGS. But here’s the thing about Allentown specifically: the hardness isn’t coming from one single source, and that’s worth understanding before you decide what to do about it.

The Lehigh Valley sits in a geological transition zone. To the north and west, you have the folded ridges of the Appalachian Mountains, made of older sandstone and shale. To the south and east, you drop into the Great Valley section, underlain by carbonate rocks — limestone and dolomite. Rainwater picks up carbon dioxide as it falls, forming weak carbonic acid. When that slightly acidic water seeps through soil and into limestone, it dissolves calcium carbonate right out of the rock. That’s the classic hard-water recipe: calcium and magnesium ions swapping into the water as it travels.

But Allentown’s water supply isn’t a simple single-aquifer story. The city draws from a mix of sources, and the hardness you see at the tap reflects that blend. Surface water in this region tends to run softer, often in the 3 to 7 GPG range, because it hasn’t had as much contact time with carbonate rock. Groundwater in the valley, however, can be dramatically harder — wells drilled into the limestone aquifer routinely test in the 10 to 20 GPG range. When a utility blends surface and groundwater to meet demand, the final hardness lands somewhere in between. At 13 GPG, Allentown’s blend is running heavy on the groundwater side.

The other contributor is treatment itself. Many municipal plants add lime or other chemicals during the coagulation and pH-adjustment process, which can actually bump up the calcium content in the finished water. So you’re looking at a combination of natural geology and treatment chemistry working together. That’s not a knock on the utility — hardness is aesthetic, not a health hazard, and the EPA doesn’t regulate it as such. It just means the water leaving your tap has a lot of dissolved mineral content, and that mineral content is exactly what leaves scale on your showerhead and spots on your glasses.

How Allentown Compares to Nearby Cities

Hardness varies quite a bit across the Lehigh Valley, even between towns that sit just a few miles apart. That’s because some municipalities rely on the same kind of limestone groundwater Allentown uses, while others pull from surface reservoirs or deeper sandstone aquifers that produce softer water.

If you live in Allentown proper, you’re dealing with water that’s harder than what you’d typically find in communities drawing primarily from surface sources. Towns that depend on the Lehigh River or local reservoirs for most of their supply tend to see lower hardness readings, often in the moderately hard range. But head a few miles south or west into areas where wells tap the carbonate valley floor, and you’ll find hardness levels that match or exceed Allentown’s.

The practical difference shows up in your appliances and your cleaning routine. On soft water, the Water Quality Association and Battelle Memorial Institute found in a 2010 study that households use up to 50% less laundry detergent and up to 70% less dish soap. That’s a real, measurable gap between Allentown’s very hard supply and a softened alternative. And the effects compound over time. Battelle Memorial Institute and the Water Quality Research Foundation found in 2009 that gas water heaters lose about 4% efficiency per 5 GPG of hardness in a typical 50-gallon-per-day household. At 13 GPG, that’s a meaningful efficiency hit before you even factor in the scale buildup. The Department of Energy notes that just a quarter-inch of scale can cut water-heater efficiency by up to 40%.

Hard water also shortens water-heater service life by roughly 30% to 50%, according to industry data. That’s not a scare tactic — that’s the mechanical reality of heating water full of dissolved calcium. The scale that forms on heating elements acts as insulation, forcing the unit to work harder and run hotter to deliver the same hot water. Over years, that extra strain takes its toll.

The Water Quality Association estimates that hard water carries a real annual cost to households through higher energy bills, faster appliance wear, and extra cleaning products. That estimate scales with your actual hardness level — you can plug Allentown’s 13 GPG into the calculator on this page to see what it means for your specific situation. It’s an industry estimate, not a measured study, but it gives you a fair sense of what very hard water is costing you versus a home with softened supply. The bottom line: Allentown’s water is on the hard end of the spectrum, and it behaves exactly like you’d expect very hard water to behave.

How does Allentown stack up against the rest of Pennsylvania? It's very hard at 13 GPG — Scranton, Philadelphia, and Lancaster sit nearby with different numbers. See the full hardest-water ranking for context.

See where Allentown sits on the Pennsylvania water hardness map →

Want the broader explainer on what hardness actually is and how it behaves? Read hard water vs. soft water, explained.