If your windows still look spotty right after they have been cleaned, you are probably looking at hard water stains. They are common on homes around Lake Minnetonka and the west metro, and often misunderstood. Here is what they are, what can be done about them, and what it costs.
What hard water stains are
Hard water carries dissolved minerals, mostly calcium and magnesium. When that water dries on glass, the water leaves and the minerals stay behind as white or cloudy spots. The usual sources:
- Lawn sprinklers that reach the windows. This is the most common cause.
- Well water. Many homes outside city water lines run on private wells, and well water is often very hard.
- Lake water splashed or sprayed onto lakeside glass.
- Hosing off the house or windows and letting the water air dry.
Why regular cleaning does not remove them
Window cleaning removes dirt, pollen and grime that sit on top of the glass. Mineral deposits are bonded to the glass surface, and normal cleaning solutions do not dissolve them. That is why stains are a separate treatment from a standard cleaning, and why they are still there after a regular wash.
Fresh stains vs. etched glass
How removable a stain is depends mostly on how long it has been there.
- Fresh deposits (one season or so) usually come off fully with the right mineral-dissolving treatment.
- Built-up deposits (several seasons of sprinkler spray) take more work, but most of the time they still come off.
- Etched glass. When minerals sit on glass for years, they can chemically eat into the surface. At that point the stain is no longer on the glass, it is in it. Etching can often be improved with polishing, but it may not disappear completely.
A quick check: after cleaning, run a fingertip over the spot. If you feel a slightly rough or raised texture, there is still mineral deposit to remove. If the glass feels smooth but still looks cloudy, it is likely etched.
Can you remove hard water stains yourself?
For light, fresh spots, yes. A mix of white vinegar and water, left on the glass for a few minutes and wiped off, works on mild deposits. Commercial mineral removers are stronger. A few cautions:
- Never use a razor or abrasive pad on a coated glass surface (some Low-E windows have a coating on the room side).
- Keep acidic cleaners off stone sills, brick and metal frames, and rinse well.
- Do not scrub hard with anything gritty. Scratches are permanent; stains often are not.
Heavy or years-old stains are where a professional treatment pays off, especially on second-story glass.
What hard water stain treatment costs
At Wash Masters, hard water stain treatment is an add-on to a window cleaning. From 2024 to 2026 it usually ran $45 to $270, depending on how many windows are affected and how heavy the buildup is. A couple of sprinkler-hit windows sit at the low end. A whole lakeside wall of glass sits at the high end. You get an exact price before we start. See what window cleaning costs for the full picture.
How to keep them from coming back
- Adjust your sprinkler heads so they do not hit the house. This one change solves most cases.
- Water early in the morning so any overspray does not bake on in the afternoon sun.
- If you rinse the house or windows, dry the glass or use filtered water.
- Keep up with regular window cleanings, so deposits get handled before they have years to etch.
The short version
White spots that survive a normal cleaning are minerals, not dirt. Fresh stains come off. Old stains can etch the glass and may not fully go away. Fix the water source, usually the sprinklers, and the problem stops.
Related questions
- How much does window cleaning cost?
- Foggy windows between the panes: what a failed seal means
- Low-E windows: how to clean them without damaging the coating
- French pane and grid windows: what to know before they are cleaned
Want us to take a look?
We clean windows across Lake Minnetonka and the west metro. Get an instant estimate, call (612) 770-8221, or see our window cleaning packages and prices.