The short answer
Hard water spots are mineral deposits (mostly calcium and magnesium) left behind when water dries on the glass. Soap and glass cleaner can't dissolve them, which is why they come back after every wash. A mild acid like white vinegar can. Soak the spots, let it sit, wipe it off, and the glass comes clean without scratching it.
Why it happens
When hard water dries, the water leaves and the minerals stay. One drop leaves a faint ring. Years of drops, from sprinklers, rain running down dirty siding, or a leaky gutter, build up into a cloudy white film that wiping won't shift.
Much of the water around Coeur d'Alene and Spokane is hard, so this is common here. The worst windows are usually the ones a sprinkler hits. If one window is far worse than the rest, look at where the water is coming from before you clean it.
What you need
- White vinegar and a spray bottle
- Warm water
- Microfiber cloths (not paper towels, which leave lint)
- A soft sponge or non-scratch pad
- A squeegee, if you have one
- Old towels for the sill
How to remove hard water spots from windows
- Wash the glass first. Plain warm water and a little dish soap. This clears the dirt so the vinegar can get to the minerals.
- Mix half white vinegar, half warm water in the spray bottle.
- Soak the spots. Spray the glass well. For stubborn spots, lay a cloth soaked in the mixture over the glass so it stays wet. Dry vinegar can't work, so keep it wet.
- Wait a few minutes. Longer for heavy buildup. You will see the film soften.
- Rub gently with a soft sponge or non-scratch pad in small circles.
- Rinse with clean water, then dry with a squeegee or a clean microfiber cloth so the water doesn't dry on the glass and leave new spots.
- Repeat on any spots that are left. Heavy, years-old buildup often takes two or three rounds. It is better to repeat than to scrub harder.
What not to do
- Don't use steel wool, a scouring powder or a rough scrubber on the glass. The spots look like dirt, but scratching the glass is permanent and the spots are not.
- Don't let vinegar sit on the frames and sills. Keep it off natural stone, and rinse it off painted, anodized or metal frames and rubber seals rather than letting it dry there. Test a small hidden spot first.
- Don't clean in direct sun. The solution dries before it can work and leaves streaks.
- Be careful with any tinted, coated or specialty glass. Some coatings are damaged by harsh cleaners or scraping. If you are not sure what yours is, test a small corner or ask before you start.
How to keep it from coming back
- Check your sprinklers. If a sprinkler is hitting the glass, redirecting it stops the problem at the source.
- Dry the glass after you clean it. Water left to air dry is how the spots form.
- Clean windows regularly. Light spots come off in minutes. Years of buildup are the hard ones.
- Know your water. If hard water is causing spots on your fixtures and appliances too, a water softener or filtration system treats the whole house instead of one window at a time.
When to call someone
If the film won't come off after a few rounds, or the glass is etched (cloudy even when wet and clean), the minerals have started to eat into the glass and household cleaners will not fix it. That is the point to have it looked at before you try anything stronger.
Hard water spot treatment is part of our window washing. If you would rather have it done properly, see our window washing or request a consultation below.