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Hard Water vs. Soft Water in Window Cleaning: Why It Matters

  • Writer: Carlos Stanza
    Carlos Stanza
  • 5 days ago
  • 4 min read
Window Cleaning in Massachusetts

Have you ever looked at freshly cleaned windows and still noticed streaks, spots, or a dull haze? It’s not always the cleaner’s fault—it could be your water.

Water quality has a direct effect on cleaning results. Hard water, which contains high levels of calcium and magnesium minerals, leaves behind mineral deposits when it dries. These deposits appear as spots, streaks, or film. In contrast, soft water—either naturally occurring or treated—has fewer minerals, making it ideal for streak-free, spotless finishes.


Understanding the difference between hard and soft water is key to getting the best window cleaning results, especially in commercial environments where appearance matters.


What is Hard Water?

Hard water contains a high concentration of dissolved minerals, primarily calcium and magnesium. These minerals naturally occur as groundwater passes through limestone, chalk, or gypsum deposits. The more minerals in the water, the "harder" it is. When hard water evaporates during cleaning, it leaves behind tiny deposits of these minerals—what we commonly see as water spots or streaks.


These deposits can:


  • Etch glass over time if left untreated

  • Attract dirt and airborne particles

  • Interfere with detergents, reducing cleaning effectiveness

  • Increase the need for aggressive scrubbing or multiple passes


In commercial facilities, this means more labor, shorter maintenance cycles, and less impressive results.


What is Soft Water?

Soft water is either naturally low in mineral content or treated through a softening process to remove calcium and magnesium ions. Because soft water leaves behind fewer mineral residues, it’s ideal for cleaning glass and reflective surfaces.


Soft water improves cleaning efficiency in several ways:


  • Reduces streaking and spotting on glass

  • Enhances detergent performance (less soap needed)

  • Protects equipment from scale buildup

  • Extends the lifespan of squeegees, washers, and glass surfaces


Professional window cleaners often use deionized (DI) or reverse osmosis (RO) treated water, which is ultra-purified and free of minerals. This type of water helps deliver truly streak-free, crystal-clear results.


How Water Hardness Affects Window Cleaning in New England

In New England, water hardness varies widely by region due to geological differences and municipal water sources. Cities like Boston, MA and Providence, RI tend to have moderately hard water, while towns in central and western Massachusetts or rural Rhode Island often experience hard to very hard water depending on local aquifers and infrastructure.

Here’s a more detailed snapshot:


  • Boston, MA: Averages 5–7 grains per gallon (gpg), equivalent to about 85–120 parts per million (ppm)—moderately hard.

  • Providence, RI: Ranges from 4–6 gpg, or approximately 68–103 ppm—also moderately hard.

  • Springfield, MA: Around 8–10 gpg (136–170 ppm)—hard water territory.

  • Worcester, MA: 6–8 gpg (102–136 ppm)—approaching hard.

  • Rural areas (e.g., Berkshire County, MA): Can exceed 10 gpg (170+ ppm), especially in well systems.


Why it matters: This variability means that even if a professional window cleaner uses perfect technique, hard water minerals can sabotage the outcome—leaving behind spots, streaks, or dull finishes.


At Jan-Ex, we test the total dissolved solids (TDS) of your water using handheld meters to determine hardness before major projects. This allows us to match the right purification system—such as DI or RO units—to your building's specific water profile and deliver optimal results the first time.


Fixing the Problem: Soft Water, DI Water, and Equipment Upgrades

To solve issues caused by hard water—like spotting, streaks, and cloudy glass—professional window cleaners rely on purification systems that remove minerals before the water ever touches the window. The goal is simple: use pure water that leaves nothing behind. Here’s how we do it at Jan-Ex—and why it makes a difference for your property.


DI Water (Deionized): Deionized water is made by running tap water through a resin filter that removes charged ions—like calcium, magnesium, and iron—responsible for mineral deposits. The result? Water that evaporates cleanly, leaving zero spots behind. To make deionized water accessible on any job site, our crews are equipped with professional-grade XERO DI Carts. These mobile units are built for soft to moderately hard water conditions, making them ideal for New England’s varied municipal water systems. With this equipment, we skip tap water altogether and deliver a crisp, glare-free finish.


RO Water (Reverse Osmosis): In areas with very hard water, reverse osmosis adds another layer of purification. RO systems force water through a semipermeable membrane, removing up to 99% of dissolved minerals, including fluoride, nitrates, and heavy metals.

Not sure what your building needs? Ask. If you’re hiring a window cleaning service, make sure they use purified water.


At Jan-Ex, we tailor our approach based on your location’s water profile and adjust accordingly to deliver consistently high-quality results.


Key Takeaways on hard water vs soft water window cleaning

If your windows consistently look “just okay” after a professional cleaning, the issue might not be your service provider—it could be the water quality. Hard water deposits are often invisible until they dry, but by then, they’ve already diminished the visual impact of your facility.

Neglecting water hardness can lead to:


  • Wasted Labor Hours: Crews may need to make multiple passes or return for re-cleans, driving up costs and reducing efficiency.

  • Tenant and Occupant Dissatisfaction: Cloudy windows can signal neglect and reduce confidence in your facility’s maintenance—especially in client-facing environments.

  • Faster Equipment Deterioration: Mineral scale buildup can damage squeegees, filters, pumps, and water-fed poles, increasing replacement frequency.

  • Avoidable Re-cleaning Costs: If windows spot or streak shortly after drying, you may end up paying for the same job twice.


The solution? Partnering with a service provider that doesn’t just clean, but understands the science behind the clean—including the impact of hard water vs soft water window cleaning. At Jan-Ex, we measure water quality on-site, deploy DI and RO systems as needed, and train our teams to adjust based on environmental variables.


Cleaner water equals cleaner windows—and that translates into better impressions, higher satisfaction, and fewer callbacks.


Schedule a Free Cleaning Walkthrough

Got window spotting issues or want to upgrade your results?

Call: (617) 294-9815


Works Cited

  • U.S. Geological Survey. (2023). Water Hardness Map of the U.S.

  • Environmental Protection Agency (EPA). (2022). Understanding Water Quality.

  • Window Cleaning Resource Association (WCRA). (2023). Best Practices for Streak-Free Cleaning.

  • Massachusetts Water Resources Authority (MWRA). (2023). Annual Water Quality Report.

  • Providence Water Supply Board. (2023). Water Quality Summary.

  • United States Department of the Interior, Geological Survey. (2023). National Water Information System (NWIS) Data. https://waterdata.usgs.gov

  • Culligan Water. (2023). What is Hard Water? https://www.culligan.com

  • NSF International. (2023). Residential and Commercial Water Treatment Reports. https://www.nsf.org

  • Jan-Ex Cleaning Field Data. (2024). Water Quality Test Results in MA/RI Service Areas. (Internal Records)

 
 
 

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