Why we clean with purified water (and why it matters)
If you've ever washed a window, watched it dry, and found faint cloudy spots where the water sat — you've met the single biggest enemy of a perfect finish: minerals in ordinary tap water. The fix isn't a stronger chemical or harder scrubbing. It's better water. Here's exactly why Davis Window Guy cleans with purified water, and why it makes such a visible difference to your glass.
The problem with ordinary tap water
Tap water isn't pure H₂O. It carries dissolved minerals — calcium, magnesium, and other solids — picked up on its way to your home. When that water dries on glass, the water evaporates but the minerals don't. They're left behind as a faint white residue: the spots and cloudiness you see after a rushed DIY clean. No matter how carefully you wipe, if there are minerals in the water, there's spotting waiting to happen.
What "purified water" actually means
Purified water (also called deionised or reverse-osmosis water) has those dissolved minerals stripped out. The result is water so pure it dries to nothing — leaving zero residue on the glass. Because there's nothing left to dry into a spot, the window dries naturally clear, all on its own, with no towel-drying required.
The simple test: let purified water dry on glass and it disappears completely. Let tap water dry on the same pane and you'll see a faint mineral ghost. That difference is the whole story.
It also cleans better
Pure water is sometimes called "hungry" water for a reason. Without minerals of its own, it actively pulls dirt and impurities off the surface it touches — so it lifts grime more effectively than you might expect, often with no detergent at all. We agitate the glass with a soft brush to loosen dirt, then rinse with a flood of purified water that carries it away and dries spotless.
Why your windows stay cleaner for longer
Here's the part people don't expect. Detergent-based cleaning can leave a thin chemical film that actually attracts dust and dirt, so windows can grime up again quickly. Purified water leaves no film whatsoever, so there's nothing for new dirt to cling to. The practical result: a purified-water clean tends to stay looking fresh noticeably longer between visits.
The secret to spot-free glass isn't a better squeegee. It's water with nothing left in it to leave behind.
Safer access to high windows
Purified water unlocks one more big advantage. Because it dries clear without towelling, we can apply it through a water-fed pole — a lightweight extension pole with a brush and water jet at the top. That lets us clean upper-storey windows safely from the ground, with no ladders against your siding or frames. It's safer for everyone and reaches glass that ladder-based methods often skip.
Gentle on your home and the environment
Because most exterior glass needs no detergent at all, there's no soapy runoff into your flower beds or down the storm drain. Purified-water cleaning is one of the most eco-friendly methods available — better for your plants, your pets, and the local watershed, without sacrificing a thing on results.
The Davis Window Guy difference at a glance
- Spot-free drying — no minerals left to cloud the glass
- Naturally lifts dirt, often with no chemicals
- No film, so windows stay cleaner for longer
- Safe, ladder-free access to high windows
- Eco-friendly with no detergent runoff
See the finish for yourself
The proof is in how the glass looks an hour after we leave — clear, even, and spotless. If you'd like to understand the wider craft, our guide to streak-free windows covers the technique, and if your glass already has stubborn marks, see how we remove hard-water stains. You can also explore our full range of services.
Want windows that dry perfectly clear? and let us bring the purified-water finish to your home.