Why Do My Windows Still Look Spotty After Cleaning?

The quick answer: Your windows look spotty because ordinary tap water contains calcium and magnesium that stay behind as white spots and streaks when the water dries. Purified water — with those minerals stripped out by deionisation or reverse osmosis — dries completely clear with nothing left behind. That is exactly how pure-water reach-and-wash cleaning fixes the problem for good.

This guide explains the simple science behind hard-water spotting, how pure-water cleaning works, why a previous cleaner or a rainy day left smears, and when you might still need a one-off first clean. For the full service detail, see our window cleaning service page.

The Science: Why Glass Dries Spotty

Water is rarely just water. Tap water in much of the South East is "hard", meaning it carries dissolved calcium and magnesium picked up from chalk and limestone in the ground. While the glass is wet you cannot see them, but as the water evaporates the water disappears and the minerals do not. They stay stuck to the glass as the white spots and cloudy streaks you are looking at.

This is why a window can be genuinely clean and still dry badly. The dirt is gone, but the rinse water itself is the problem. It is the same reason a glass from the dishwasher dries with cloudy marks, or your kettle furs up — minerals left behind once the water has gone.

How purified water solves it

Pure-water cleaning removes those minerals before the water ever touches your windows. The water is passed through deionisation (DI) resin and/or reverse osmosis (RO) filtration, which strips out the calcium and magnesium. The result is "hungry" water: with nothing dissolved in it, it actively lifts dirt and minerals off the glass, and crucially, when it dries there is nothing left to leave a mark. The glass dries spotless on its own — no squeegee, no buffing, no chemicals.

What Reach-and-Wash Actually Is

Reach-and-wash (also called the water-fed pole or WFP method) is the modern standard for residential window cleaning, and it is what we use. Here is how it works:

• Purified water is pumped from a tank up a long, lightweight carbon-fibre pole.
• A soft brush head at the top scrubs the glass, frames and sills.
• The same pure water then rinses everything, top to bottom.
• The glass is left to dry on its own — spotless, because the water has no minerals in it.

Because it is all done from the ground, there are no ladders leaning on your gutters, conservatory or flowerbeds, and upper-floor windows are reached safely without scaffolding. The brush also reaches the frames, sills and doors, so they are cleaned every visit — something a traditional squeegee simply does not do.

Why Your Last Cleaner (or the Rain) Left Smears

If your windows looked worse after a clean, it is usually one of three things:

1. They used tap water. Even a careful clean dries spotty if the rinse water is full of minerals. This is the most common cause.
2. They used a squeegee with detergent. Traditional cleaning can leave soapy residue or fine edge smears where the blade lifts, especially in cold or windy weather.
3. They skipped the frames. If only the glass is cleaned, dirt sitting on the frames and sills runs back down onto the glass the next time it rains, so the "clean" looks short-lived.

The same goes for rain itself: a downpour after a tap-water clean redeposits dust and lets mineral-laden droplets dry on the surface. Pure-water reach-and-wash sidesteps all of this — clean rinse water, no detergent, and frames done every time.

Traditional Squeegee vs Pure-Water Reach-and-Wash

Here is how the two methods compare on the things that actually decide whether your glass stays clear.

Traditional cleaning still has its place for internal glass and ground-floor shopfronts, where a careful applicator and squeegee work well. But for exterior residential glass that needs to dry spotless, pure water wins on every line that matters.

When You Still Need a One-Off First Clean

Pure water dries spotless — but it is not magic on neglected glass. If your windows have years of built-up grime or heavy hard-water staining baked on, the very first clean may need extra work to strip that history away before a regular round will dry perfectly every time.

We will always be straight with you about this. If your glass needs a one-off restorative clean first, we say so up front rather than promising instant perfection and leaving you disappointed. After that first clean, a regular pure-water round keeps the glass clear with a quick, low-cost visit each time — see how often you should clean your windows for choosing the right interval, and window cleaning prices in Surrey for what it costs.

Safety and Eco: Why Ground-Based Pure Water Is the Standard

Reach-and-wash is not just about spotless glass — it is the safer, greener way to clean windows.

• No ladders, no working at height. Under the Work at Height Regulations 2005, work should be done from the ground where reasonably practicable. Water-fed poles let glass be cleaned from ground level rather than balancing on ladders, which is the direction the whole industry has moved (HSE; Federation of Window Cleaners).
• Recognised best practice. The HSE and the Federation of Window Cleaners jointly publish guidance on safe water-fed pole use, and workplace safety in window cleaning was raised in UK Parliament in December 2025, underlining that ground-based working is the industry's safety direction.
• Genuinely eco-friendly. Pure-water systems use no detergents or chemicals, so nothing harmful runs into your drains, soil or flowerbeds — just filtered water and a soft brush.

Frequently Asked Questions

Why do my windows look spotty after cleaning?

Ordinary tap water contains dissolved calcium and magnesium. When water dries on the glass, the water evaporates but those minerals stay behind as white spots and streaks. The cleaner can leave the glass perfectly clean, but as soon as tap water dries it leaves spotting. Purified water with the minerals removed dries clear with nothing left behind.

What is pure water window cleaning?

Pure water window cleaning, also called reach-and-wash, pumps 100% purified water up a telescopic carbon-fibre pole with a soft brush head. The brush scrubs the glass and frames, then the pure water rinses everything. Because the minerals have been removed by deionisation or reverse osmosis, the water dries completely spotless on its own with no chemicals, squeegee or ladders.

Why did my last window cleaner leave smears?

Usually one of three things: they used tap water, which dries with mineral spots; they used a squeegee that left detergent residue or edge smears; or they cleaned the glass but skipped the frames, so dirt from the frame ran back onto the glass at the next rain. Pure-water reach-and-wash avoids all three.

Do I still need a first clean if pure water dries spotless?

Sometimes, yes. If glass has heavy mineral staining or years of built-up dirt, it may need a one-off restorative first clean before a regular pure-water round will dry perfectly every time. We set that expectation up front rather than promising instant perfection on neglected glass.

Is pure water window cleaning better for the environment?

Yes. Pure-water systems use no detergents or chemicals, so nothing harmful runs into your drains, soil or flowerbeds. The only thing touching your glass is filtered water and a soft brush, which is a genuine eco and safety benefit, not greenwashing.

Get Your Free Quote

We are a small Redhill 2-man crew — honest, plain-spoken, the same faces every visit. If pure water alone will not get your glass perfect, we will tell you. We cover Redhill, Reigate, Crawley, Horley, Dorking, Banstead and all areas within about 20 miles of RH1. Tell us your postcode for a free, no-obligation quote.

Get My Free Quote Call 01737 652 515

Related guides: Window Cleaning Service | How Often to Clean Windows | Window Cleaning Prices in Surrey | Gutter Cleaning Guide

Sources

The safety and method points below are sourced from the industry body, the HSE, and UK Parliament. The hard-water spotting explanation reflects how deionised/RO water works in practice.

1. Federation of Window Cleaners — Safety in Window Cleaning using Water Fed Pole Systems. Ground-based pure-water working as industry best practice. f-w-c.co.uk — WFP safety guidance (PDF). Accessed 16 June 2026.
2. Health and Safety Executive (HSE) — Window cleaning health and safety topics. Work at Height and ground-based working guidance. hse.gov.uk — window cleaning. Accessed 16 June 2026.
3. UK Parliament (Hansard) — Window Cleaning Industry: Workplace Safety debate, 17 December 2025. Confirms ground-based WFP as the industry's safety direction. hansard.parliament.uk — window cleaning safety debate. Accessed 16 June 2026.