Cobb County Water Is Soft — So Why Do You Have Hard-Water Spots?

The soft-water fact

The Cobb County–Marietta Water Authority reports treated water hardness around 31.7–35.1 milligrams per liter — roughly 2 grains per gallon, firmly in 'soft' territory, with total dissolved solids around 71–74 mg/L. If a cleaner blames 'Marietta's hard tap water' for your spotted glass, they're reading a national script, not your water report.

The real culprits

Well water, where a home has it, is untreated and can be genuinely hard. Irrigation is the big one: sprinkler systems pull the same supply but concentrate minerals through daily evaporation cycles on hot glass — and systems on wells or retention sources are harder still. Pool splash adds its own chemistry. The pattern gives it away: spots that map exactly to a sprinkler arc or a pool's splash zone, worst on the sunniest panes.

What can be done

Fresh deposits sit on the surface and usually lift with professional treatment; years-old spots can etch into the glass and become permanent — which is why our hard water stain removal service starts with a test spot and a straight answer. Then fix the source: adjust the sprinkler aim, and put the affected panes on a schedule so deposits never get another season to bake.

The wider lesson

Local facts beat national scripts — in water, in pollen timing, in what a Marietta clean should cost. It's the standard we hold this whole site to, from the cost guide to the neighborhood pages.

Reading the pattern on your glass

Spots are evidence, and their pattern usually names the source before any test does. A fan-shaped band of white dots across the lower half of a pane, worst on the sunniest elevation, is the classic signature of a sprinkler head throwing treated or well water onto hot glass day after day, each cycle evaporating and leaving its minerals behind. A tight halo around a pool or hot tub points to splash chemistry. Uniform faint spotting on every pane, by contrast, is more often pollen, dust and rain residue — the ordinary Marietta film that a normal clean removes — rather than true mineral scale at all.

That distinction decides the remedy. Surface deposits from a season or two of overspray generally respond to professional hard-water treatment. Deposits left for years can etch into the glass surface itself, and etched glass does not polish back to new; any cleaner who promises otherwise before testing a spot is guessing with your windows. The honest sequence is a test spot on the worst pane, a straight answer about what lifted and what did not, and only then a price for the rest.

Prevention is cheaper than either. Aim irrigation heads so arcs land on planting beds rather than glass, keep the worst-hit panes on a regular cleaning schedule so deposits never get a second season to bake on, and treat new spotting early — while it is still on the glass instead of in it. Keep a note of which panes spot fastest after each irrigation cycle; that short list becomes the priority set for treatment and for the maintenance schedule that keeps new deposits from hardening into the glass.

Frequently asked questions

Is Cobb County tap water really soft?

Yes. The Cobb County–Marietta Water Authority reports treated-water hardness around 31.7 to 35.1 milligrams per liter — roughly two grains per gallon, firmly in soft territory, with total dissolved solids around 71 to 74 mg/L.

If the water is soft, why are my windows spotted?

Because the water hitting your glass is usually not tap water used once — it is irrigation overspray evaporating daily on hot panes, well water where a home has it, or pool splash. Repeated evaporation concentrates even modest minerals into visible scale.

Can hard-water spots be removed completely?

Fresh surface deposits usually lift with professional treatment. Years-old deposits can etch into the glass and become permanent, which is why Resiclean starts with a test spot and a straight answer before quoting the whole house.

Related reading

• Pure Water vs Squeegee: Which Is Right for Your Marietta Home?
• Window Cleaning Cost in Marietta, GA: Three Worked Examples (2026)
• Post-Pollen Window Cleaning: When to Book in Marietta (Late April, Not Mid-Peak)
• Hard Water Stain Removal — the Resiclean service page for this topic

Sources

• Cobb County–Marietta Water Authority — Annual Water Quality Information
• Cobb County Government

Next step: get a free, firm estimate for your own home — call (770) 846-5651 or send the form. See what window cleaning costs in Marietta and what customers say.