How to remove hard water stains from glass

To remove hard water stains from glass, apply white vinegar or a limescale remover, let it sit so it can dissolve the mineral deposits, then wipe and rinse. Hard water stains are limescale, the chalky residue left behind when mineral-rich water dries on the surface. A mild acid breaks it down safely; the key is giving it time to work rather than scrubbing with anything abrasive.

What hard water stains actually are

Much of the UK, including parts of the Midlands, has hard water, meaning it carries dissolved calcium and magnesium. When that water dries on glass, the minerals stay behind as cloudy white spots and streaks. Left too long, limescale can etch into the surface and become much harder to remove, so dealing with it early matters.

How to remove light to moderate stains

• Spray or wipe the glass with white vinegar (warmed slightly works faster) or a dedicated limescale remover.
• Leave it to dwell for several minutes so the acid can dissolve the deposits.
• Wipe with a non-scratch cloth or sponge, re-applying to stubborn areas.
• Rinse with clean water and dry with a microfibre cloth or squeegee for a streak-free finish.

For stubborn, built-up limescale

Heavy deposits may need a second application and a little dwell time. A paste of bicarbonate of soda can add gentle, non-scratch lift after the acid has softened the scale. Always rinse thoroughly afterwards. If the glass still looks cloudy once dry and clean, the surface may be etched, that is permanent damage the deposits caused, not remaining scale.

What to avoid on glass

• Abrasive pads, wire wool and scouring cream: they leave fine scratches that cloud the glass for good.
• Blades and scrapers: easy to scratch and best left to professionals on the right glass.
• Leaving acid on too long: rinse it off; do not let it dry on the glass or surrounding metal fittings.

How to stop hard water spots coming back

Prevention is far easier than removal. Keep a squeegee in the shower and clear the screen after each use; wipe windows dry after cleaning; and deal with dripping outdoor taps or sprinklers that repeatedly wet the same glass. For windows generally, our guide to why windows look streaky covers drying technique, and how often to clean windows sets a sensible schedule.

When to bring in a professional

Exterior windows, conservatory glass and hard-to-reach screens with years of built-up scale are awkward and slow to treat by hand. Professional window cleaning uses purified water and the right technique to leave glass spot-free, and can advise whether badly affected glass can be restored or has etched. For conservatories, see our conservatory cleaning service.