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

Why Is Troy’s Water So Hard?

Troy’s water measures 7.31 GPG (125 ppm), which puts it right at the “hard” threshold. That level of hardness doesn’t come from some exotic source; it comes from the everyday reality of where the water travels before it reaches your tap. The water itself is surface water, drawn from the Great Lakes system, and that detail matters more than most people realize.

Here’s the thing about Great Lakes water: it’s not the soft, pristine rainwater people imagine. The lakes are massive, but they’re also the collecting bowl for a huge drainage basin. Rain and snowmelt run over and through limestone, dolomite, and glacial till across Michigan and Ontario before ever reaching the lake. Those rocks are essentially compressed calcium and magnesium carbonate. Water is a decent solvent, and as it moves across that geology, it picks up dissolved minerals along the way. By the time it sits in the lake and gets drawn into a treatment plant, that water is already carrying a measurable load of hardness.

Troy sits in Oakland County, which is squarely on top of the kind of glacial geology that makes this worse, not better. The last ice age scraped up and redeposited layers of crushed limestone and dolomite across the region. So you’re not dealing with a single underground aquifer with a simple mineral story. You’re dealing with surface water that has already spent weeks or months in contact with carbonate-rich sediment and bedrock. That’s the whole story: the water isn’t hard because of something the utility does to it. It’s hard because the entire watershed it comes from is made of the stuff that dissolves into hardness.

One thing worth being clear about: hardness is not a regulated contaminant. The EPA classifies it as an aesthetic issue under its Secondary Maximum Contaminant Level, which means it’s about scale, soap scum, and appliance wear, not about safety. That 7.31 GPG reading is enough to leave white deposits on fixtures and make soap less effective, but it’s not a health concern. It’s a mineral-load issue, plain and simple.

How Troy Compares to Nearby Cities

Troy’s 7.31 GPG puts it in the middle of a fairly consistent regional picture. Because the water source is shared across the metro area, nearby cities drawing from the same Great Lakes surface supply tend to land in the same general hardness range. That’s not a coincidence. When multiple municipalities pull from the same lake or the same connected intake system, they’re starting with essentially the same raw water chemistry. Treatment differences can shift the numbers a little, but the underlying mineral content is regional, not local.

That means if you’ve got family in neighboring Oakland County communities, their water is probably behaving in similar ways. You might see a point or two of difference on a test strip, but you’re not going to find one city with soft water and another with extreme hardness right next door. The geology underneath the whole region is uniform enough that the water chemistry follows suit.

The practical side of that comparison is simple. If you’re used to Troy’s water and you move a few miles away, don’t expect a dramatic change. Scale buildup on showerheads, the need for more dish soap, the film on glassware, all of that is going to look familiar. The USGS notes that roughly 85% of U.S. households deal with hard water, and the national average sits around 7.3 GPG. Troy’s 7.31 GPG is almost exactly that national average, which makes it a textbook example of typical American hard water rather than an outlier.

That said, the consequences are real even if the number is average. According to the WQA and Battelle Memorial Institute’s 2010 detergent study, soft water can cut laundry detergent use by up to 50% and dish soap by up to 70%. And on the appliance side, Battelle and the Water Quality Research Foundation found that gas water heaters lose about 4% efficiency for every 5 GPG of hardness, while the DOE notes that just a quarter-inch of scale can cause up to 40% efficiency loss. So Troy’s water isn’t extreme, but at 7.31 GPG, it’s firmly in the range where scale is going to form and cleaning products are going to work harder than they need to. The WQA estimates that hard water carries a real annual cost across energy, appliance wear, and cleaning supplies, and that figure scales with your actual hardness level. You can run your own numbers with the calculator on this page to see what it means for your household.

How does Troy stack up against the rest of Michigan? It's hard at 7.31 GPG — Lansing, Dearborn, and Livonia sit nearby with different numbers. See the full hardest-water ranking for context.

See where Troy sits on the Michigan water hardness map →

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