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How To Remove Hard Water Stains from Windows

What Causes Hard Water?

All water contains minerals of some sort, which is what defines “hard water.” The higher the mineral content, the harder the water. Some areas, like those where water travels through limestone, naturally have more mineral deposits. However, water can also pick up minerals and contaminants as it travels through pipes. This is why water hardness not only varies from city to city, but also building to building.

Hard water collects on all kinds of hard surfaces – including glass – which leads to deposits. Depending on the mineral content, the frequency that the surface is being pounded by hard water (think sprinkler system), and the amount of time between cleanings, hard water stains range in difficulty to remove.

A good resource to help your customers better understand this is Understanding and Managing Hard Water at Home: Health and Cleaning Considerations.

Hard Water Stain Removal

As JRC Senior Sales Manager Doug Apt explained, "Not all hard water stains are created equal. That's why we carry 13 different products for removing hard water stains."

JRC Senior Sales Rep Jenny Bahn said she likes to compare hard water stains to kitchen knives. "In the kitchen, you have butter knives, steak knives, butcher knives, etc. You wouldn't need a butcher knife to cut butter, and you wouldn't need a butter knife to cut open a coconut." It's the same idea with hard-water removing chemicals.

We recommend starting with the "butter knives" -- i..e., your cream/paste products and your powder cleaners -- then work your way up to the "steak knives" (i.e., mild acids), only turning to the "butcher knives" (stronger acids) if absolutely necessary.

Scrubbing Pads

Along with your hard-water stain removal chemicals, you’ll also need scrubbing pads. The go-to pad is the white nylon non-scratch pad.

For more aggressive scrubbing that is still non scratch, go to 0000 steel wool, or our preference, bronze wool, because it lasts longer and does not rust.


Creams and pastes are mildly aggressive. While they do not typically scratch the surface, it can happen, so use caution.

Diamond Magic is a creme compounded with special formulation and real diamond dust to make a formidable stain remover and polishing compound. The secret of Diamond Magic is the use of multi-level, sub-micron diamond dust, compounded with a compatible paste, creating a synergy that cleans and polishes unpainted metal, glass, tile, and porcelain to a near-new condition.

Bio Clean Water Stain Remover works on glass that has Stage 1 corrosion, i.e., glass with light corrosion, with little or no damage to the glass. This includes removal of water spot stains, mineral deposits, soap scum, mildew, rust, tree sap, paint overspray, and oxidation deposits from windows, glass, shower doors, and more.

Titan A1 Hard Water Stain Remover is for use in the removal of silicas, cement leach, acid rain, and mineral deposits from glass. A nontoxic, water-based biodegradable soft cream, A-1 contains no acids or abrasives. Easy to apply with a scrub pad, felt pad, or find steel wool by hand or oscillating buffer (8,000 - 11,000 rpm).

How to Clean with Creams/Pastes:

  • Clean the surface with a damp towel to remove dirt and grime. This will help you avoid scratching and possible permanent damage.

  • Apply the product with a dry cloth, sponge, nylon pad, soft bristled brush, or oscillating buffer.

  • Press firmly, loosening the stain with a circular rubbing action.

  • Rinse with water until the glass is residue free.

  • Clean and squeegee the window.

  • Repeat the application as needed until the surface is clean and spot free.


How to use powders:

  1. Mix with water to make a paste.
  2. Apply to the surface using a soft, wet towel or a white nylon scrub pad

Sorbo Hard Water Residue Remover was developed especially for cleaning and removing stains from glass and tile surfaces. Primarily Sulfamic acid in a powder form, Sorbo powder goes to work quickly on stains. Sorbo Stain Remover takes off hard water stains, building run-off and sprinkler stains from windows and other glass surfaces like shower doors.

Mr. Hard Water Stain Remover is an eco-friendly, industrial strength, super-fine, organic, acid/chemical free cleaning, polishing, and hard water removal powder designed for use on glass, tile, polished stone, polished metals, and more. It cleans without etching, scratches, or swirls because it is milled to a super-find powder that can reach micro-pores.


IMPORTANT: When using acids, wear personal protective equipment (PPE)! This includes acid-resistant gloves, safety goggles, a mask, and rubber boots. These are professional-grade acids and can cause injury.

Acids can cook or smoke float glass. We highly recommend testing any acid you use on a small area of the glass to ensure it will not damage the glass, then get a waiver signed. (We have samples you can use.)

Because water is hydrophobic, you'll need to continuously reapply acid. Withe severe hard water, the ideal dwell time for acid is 5-7 minutes on the glass, and it needs to never dry on the glass. This means you have to keep a scrubbing action going continuously, and you should keep a pump-up sprayer nearby to help lightly moisten the glass. However, try not to dilute the acid too much; it performs better at full strength.

We recommend starting with a milder acid, like OneRestore. This is a breakthrough detergent that provides remarkable versatility, cleaning power and safety all in one product. It is capable of removing the deepest water hardness and pollution stains, and mineral and metal oxide stains from a wide variety of surfaces. It is an effective coating remover and safely cleans glass and anodized aluminum when used as directed. Hydrochloric Acid based: Make sure you wear gloves with any type of harsher acid.

Clearview 200 is a stronger acid that we like because it comes on a textured wipe that is infused with a proprietary solution to effectively remove Stage 1 and 2 moderate hard water stains while reducing exposure from splash and runoff.

The strongest, most potent product that we carry for hard water stains is Winsol's Crystal Clear 550, which is used for glass that won't come clean with other products. It's designed to remove stage 1 alkaline particles, exhaust particles, chemical and mineral deposits, water spots, and runoff from brick, mortar, and concrete on glass.

Warning: Crystal Clear 550 contains both hydrochloric and hydrofluoric acids, which will smoke or cook float glass. (More on this in an upcoming blog.) You should wear proper PPE when working with this product!

An add-on service you can provide in areas where the glass is prone to hard water or other staining is to add the ProTool 3-Star Barrier.

Barrier is an easy-to-mix, easy to apply surface protectant. It forms a bond to glass and other nonporous surfaces to form an invisible molecular barrier that protects the surface against scratching while repelling liquids and dirt between cleanings. If you're cleaning the glass as often as quarterly to every 6 months, this is the protectant to choose