Hard water spots are one of the most common window complaints — and one of the most misunderstood, since the fix that works for light spots can make heavy ones worse.
Why they show up in the first place
Hard water stains come from mineral-laden water — sprinkler overspray is the most common source — that evaporates on the glass and leaves the dissolved minerals behind. The longer that mineral film sits and gets baked on by sun exposure, the harder it becomes to remove.
For light to moderate spots
Vinegar solution: Mix equal parts white vinegar and water in a spray bottle (or use vinegar straight for tougher spots). Spray it on, let it sit a few minutes to break down the minerals, then wipe.
Rinse with distilled water, not tap water. This part matters — rinsing with regular tap water can leave new mineral spots behind while you’re trying to remove old ones.
Dry immediately with a squeegee or microfiber cloth. Water that’s allowed to air-dry is exactly how these spots form in the first place.
For tougher, more established spots
A baking soda paste — just enough water mixed in to make it spreadable — applied with a damp cloth in gentle circular motions handles staining that vinegar alone doesn’t touch. Rinse thoroughly and dry immediately afterward, same as above.
When it’s time to call a professional instead
If spots resist both methods, the minerals have likely etched into the glass surface itself rather than sitting on top of it — at that point, no amount of scrubbing at home will fully remove them, and pressure washing can make it worse by forcing minerals deeper into the etching. Professional-grade mineral removal treatment is built for exactly this, without risking the glass.
Preventing them going forward
The simplest fix is also the most overlooked: dry windows with a squeegee immediately after they get wet — from cleaning, rain, or sprinklers — rather than letting water evaporate on its own.
See our window cleaning page for our streak-free process, or request a free quote if hard water staining has built up past the DIY stage.