The Real Secret to Streak-Free Windows (It's Not the Squeegee)
2026-02-05 · WaveWash Ventura
Everyone blames technique. The truth is, streaks usually start with your water. Here's what professional crews know that DIY guides miss.
Streaks aren't a technique problem
Search 'how to clean windows without streaks' and you'll find a hundred articles arguing about squeegee angle, microfiber vs. newspaper, and whether to clean in direct sun. All of that matters a little. But the single biggest cause of streaks has almost nothing to do with technique — it's the water itself.
The mineral problem
Ventura County tap water is hard, meaning it carries dissolved minerals. When that water dries on glass, the minerals stay behind as a faint, uneven film — and that film is exactly what you see as streaking and spotting. You can squeegee perfectly and still get streaks, because they form as the last traces of water evaporate, after you've already walked away.
This is why professional crews use purified or deionized water. Strip the minerals out before the water touches the glass, and there's nothing left to dry into a streak. The window can literally be left to air-dry and come out spot-free.
What this means for your home
If you clean your own windows and can't beat the streaks, it's probably not you — it's the water. For exterior glass especially, a purified-water system is the difference-maker. It's also gentler on the rest of your home: no soapy runoff staining your stucco, no minerals etching your frames.
The bonus: glass stays clean longer
There's a second benefit that matters a lot in our dusty climate. Because purified water leaves no residue, there's no film for new dust to cling to. Glass cleaned this way doesn't just look better the day it's done — it stays clearer for weeks longer than glass wiped down with tap water and spray cleaner.