Timber - PVC - Aluminium - Windows, Doors & Conservatories in Hampshire
Hard Water Window Damage
Hard Water Window Damage
Our region sits on massive Chalk Aquifers. This means tap water in Hampshire is loaded with dissolved Calcium Carbonate. When this dries on your windows, it physically etches the glass.
1. The Rain vs. The Hosepipe
We often hear customers ask: “Rain is water, so why doesn’t rain leave white spots?” The answer lies in the journey the water takes.
Rain is essentially distilled. It has almost zero mineral content. Because it is naturally soft (and slightly acidic), it dries clean. Rain is not the enemy.
Tap water has spent 50 years underground filtering through chalk. It contains ~300mg of rock per litre. If you wash your windows with a hose and let them air dry, you are painting them with liquid chalk.
“I never use a hose, but I still get spots!”
This happens when soft rain hits a concrete lintel, stone sill, or rendered wall before it hits your glass. The rain dissolves minerals from the building material itself, turning it “hard” just seconds before it dirties your window.
2. The Danger Map: Is Your Town “Aggressive”?
Hard water is measured in Parts Per Million (PPM). According to the Southern Water Hardness Checker, our region consistently ranks as “Aggressively Hard.”
🚰 Tool: Check Your Risk Level
Select your nearest town to see your specific data:
⚠️ Status: AGGRESSIVELY HARD (300+ PPM)
The Risk: Extreme. Friction hinges can seize up within 5-7 years without lubrication. Glass is at risk of “Stage 2 Corrosion” (Etching) if hose water is left to dry.
⚠️ Status: HARD (200-280 PPM)
The Risk: High. Limescale will build up on black rubber seals, turning them grey. Friction hinges will become stiff and require annual oiling.
✅ Status: MODERATE / SOFT
The Risk: Low. You are lucky! Your windows will require significantly less maintenance than those further north in the county.
3. The Science of Etching (Ion Exchange)
Why can’t you just scrub the spots off? Because they aren’t just on the glass.
If alkaline limescale sits on glass (which is made of silica) for too long, it triggers a chemical reaction called Ion Exchange. The calcium bonds with the sodium in the glass, effectively creating microscopic craters. The glass itself is pitted. This is why “prevention” (drying the glass immediately) is the only cure.
| Cleaner Type | Ph Level | Effect on Limescale |
|---|---|---|
| Standard Blue Spray | ~10 (Alkaline) | ❌ Fail. Polishes dirt but seals in the minerals. |
| Washing Up Liquid | ~7 (Neutral) | ❌ Fail. Good for mud, useless for chalk. |
| White Vinegar | ~2.5 (Acidic) | ✅ Success. Dissolves Calcium Carbonate on contact. |
50/50 Vinegar Glaze
Ingredients:
- 50% White Distilled Vinegar (The Acid)
- 50% Distilled Water (The Solvent)
- 1 Drop Dish Soap (Breaks surface tension)
Note: Do not use tap water! If you clean with tap water, you are adding more chalk as you clean.
The Method:
- Spray directly onto the “white spots” on the glass.
- Wait 3 minutes. This dwell time is crucial—you must let the acid eat the calcium.
- Wipe with a microfibre cloth.
- Buff dry immediately. Never let hard water air-dry on glass.
4. The “Silent Killer”: Drainage Channels
There is a hidden danger most people miss. At the bottom of your uPVC frame, hidden inside the rebate, are “Drainage Channels” designed to let water flow out.
The Hard Water Effect: In Hampshire, these channels often calcify. Like a blocked artery, the chalk builds up until the water can’t escape.
The Result: In winter, trapped water freezes, expands, and blows the seals or cracks the frame.
The Fix: Once a year, pour a little warm water (mixed with the vinegar solution above) into the tracks to keep them flowing.
Window seized shut? We can often replace the hinges without buying a new window.
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Mark Pearce is a highly experienced specialist in the double glazing industry, having built his knowledge from the ground up through hands-on experience in installation, manufacturing, sales, and business management. Beyond his role at KJM, Mark is a keen blogger, writer, and traveller, often sharing insights on the latest innovations in the home improvement industry.
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