Sometimes the water from the sink or a sprinkler can make stubborn water spots on your windows. This guide is about removing hard water spots.
Read and rate the best solutions below by giving them a "thumbs up".
My husband read so many solutions on removing hard water spots on windows, but nothing ever worked for him. The windshield on our motor home was so stained from the water that would run down it, that we tried everything on the market just like so many others. We bought so many products from acid wash, scrub with SOS, to Comet.
I always use Scrubbing Bubbles for everything in my house. I told my husband for so long to try Scrubbing Bubbles but he always told me, "No that isn't going to work", until one day when he was frantic, he did try Scrubbing Bubbles along with extra fine steel wool. He couldn't believe his eyes. The glass is crystal clear and just like new. Now he won't use anything else just like I won't use any other product except for Scrubbing Bubbles inside.
So every one who is at their worst with hard water spots please use this product. It really does work. I know this sounds like a infomercial, just try for yourself.
Scrubbing Bubbles Fan!
By Peewee the Cat and Family from San Bernardino
Use shower cleaner, SOS pad, and water.
By Ela B. 
I have had very hard water spots on my windows from the irrigation system for a year. I just tried Colgate Toothpaste as suggested by Chris on ThriftyFun. My windows are now perfectly clear and it was so easy! I put a little Colgate Toothpaste on a damp paper towel, rubbed it on the glass in circular motions, then I rinsed with vinegar water (anything that would clean the paste off should work). and dried thoroughly. The glass is sparkling!
To remove hard water spots from glass, you'll need:
First off let me say that nothing else worked. I tried everything from glass cleaner with vinegar to straight vinegar. I even tried Scrubbing Bubbles (as found here on this site), but nothing worked. Then the light bulb! I grabbed the above listed items and tried one window - beautiful.
How to: pretty straight forward - pour cooktop cleaner onto non scratch scrubbing sponge (I used Weiman cooktop cleaner and a Weiman scrubbing pad - red). Work in a circular motion covering the window. Use the wet rag to wipe clean the edges of the window frame. Buff the window with the microfiber towel. Presto!
By jsruff08 
My car windows were covered in hard water spots after mistakenly parking near a sprinkler at work on a hot summer day. I have washed my car three times and paid close attention to the windows, but had no luck getting the spots off. Today I decided to see what I could do with household products.
Here's what I used:
Here's what I did:
Step 1: Use a small amount of toothpaste, rubbed onto the worst of the water spots, and buff with a dry paper towel. Pay close attention to the areas where the spots are the worst. If necessary, dampen the paper towel a little once the tooth paste gets too dry. I didn't get the paper towel TOO wet because I didn't want to drip tooth paste onto the body of the car. Not sure what that would do to the paint job.
Step 2: Dampen the microfiber towel with the mixture of vinegar/water/dish soap, and use it to clean the window overall. Use a little extra elbow grease where you can still see the spots.
Step 3: Once you have gotten the toothpaste up, flip the towel over and wipe until the streaks are gone.
After following these three steps, my windows are spot-free and shiny! Now, I'm going to go back and put on some Rain-X on my windows to prevent this from happening again.
I water my lawn with very hard water in a very windy area. There is almost no way to keep the water off my windows every time I water. In the past, I had used ammonia to wash the windows and vinegar to get rid of the hard water stains.
Then last year I broke my arm and missed a whole year of washing windows. This spring the hard water stains seemed to have become part of the glass. Then I thought about the way I clean my cooktop.
I first washed the windows with ammonia/water solution, then wiped vinegar on a section of the window. I then scraped the glass in that section with a single-edged razor blade. The stains were removed with very little effort.
My brother parks his car on the street and every night the sprinklers go on. When he wakes up in the morning, he has water spots on the right side of his car. He tried washing his car but the spots would not come off. He also tried Windex, white vinegar, brake cleaner, anything you could think of!
Then my mom said, "Hey, try this Ajax!" With a little bit of water, the spots came right off! So the trick is AJAX!
Hope this helps.
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Here are questions related to Removing Hard Water Spots on Windows.
How do you remove water marks on the exterior side of house windows?
I bought a car recently and it has water spots all over the car. It's so bad that it has become part of the paint job, and the windows are so bad that you can barely see out of them.
I've tried the vinegar and that does not work. I don't think the owner before ever washed the car. So I'm worried I will not find anything to work on something this severe. I even tried scrapping with a razor. It got the dirt layer off but the spots are not leaving. Please I need the help with my situation!
There are so many Scrubbing Bubbles products - which one do you use with the fine steel wool?
I'm not sure what they are called, but I'll say I have windshield streaks. They are lines going straight down all across. This happened during the winter. Anyone know what this is, or how to remove them?
By Donna 08/03/2013
"Full strength" white vinegar and a newspaper (not a paper towel) - wadded up newspaper does a better job.
I have parked my car below a water tank. Once the water tank filled; the extra water will fall on the car. So salt water deposited on my car. How do I clean salt deposits off my car?
By N Senthil
I had washed my car in the afternoon and the water drops dried. I was unable to remove the stains. So how can I remove the stains? My car is a Maruti Suzuki swift.
By Louise B. 06/14/2013
Wash with vinegar.
How do I remove hard water spots from glass?
By Barbara G.
By Nancy F. 08/09/2011
Someone once told me that oven cleaner would do it. I have never tried it.
How do I get water spots off the outside of a picture window?
By Louise B. 08/08/2011
Are they water spots caused by hard water, such as that from a sprinkler, hitting your window? If so, vinegar should remove them. Do not dilute when you use it. I would put it in sprayer, and spray on full strength.
I have four 10'X6' windows (all glass) and about 15 smaller windows of different sizes that get sprayed by water containing calcium, and various other minerals that will not wash off with soap or other washer solutions. I presently use dish soap and hot water and a bit of CLR added. I have used an ammonia solution, vinegar, and rubbing alcohol. Nothing really phases the stains even though the windows get clean, they still show those hard water stains.
We use ditch water to irrigate the lawn by a sprinkler system. Help! I also used automotive products and the products that you are supposed to put on and hose off. They definitely made no difference other than to clean.
By Lula C. from Cimarron, CO
I am not sure using CLR would be good for the environment, but as long as you keep it off the ground and wear gloves so you are protected... I can also suggest a razor blade to remove any remaining film/crust from hard water stains. Also found this: http://www.ehow.com/how_5412240_remove-hard-water-stains-windows.html
All my windows have spots on them and that makes it difficult to see. I have deep, deep water. I have tried many cleaners. Please help.
By Karen Redlin 06/28/2011
If you have hard water spots on your windows they will be hard to clean. Lime away does work but I don't like the harsh chemical. Spray your window with a window cleaner and use a scraper with a blade (the kind you use to remove paint on a window) to scrape over the hard water spots. Be careful to keep the blade flat and not scratch the window. Wipe the window and spray any spots you missed and scrape these away. If you have a huge build up, ammonia water works better than window cleaner but then again, you are dealing with harsh smelly chemical.
I've tried to clean my house windows with cleaners such as Windex, Bon Ami, vinegar, Colgate toothpaste, Cascade, Dawn, and baking soda. They are stained with water spots and grime. We live on the golf course and I don't know what all they spray on the fairway, etc., but I can't get my windows clean. Please help!
By Bill from Fontana, CA
By Kolleen 02/14/2011
What you are describing as water spots sounds more like Sticker spots. Sticker is a chemical that somewhat water proofs another chemical like fungicides. The make-up of this stuff is pretty simple it's like Elmers glue and dish soap, something I have used when landscaping in large complexes.
To remove Sticker spots use alcohol, rubbing will work as will alcohol based hand sanitizers. You may also have to use a light abrasive like baking soda. Dampen a cloth with the alcohol or rub the sanitizer on the window and scrub ( you may want to let the sanitizer sit to work it's way into the stains) then polish with the baking soda and rinse. It may take more than one application to remove all this stuff.
After you get the windows clean seal the glass with a rainex type product. Also check into having the golf course clean up their mess, if this has gotten onto your windows via a pesticide application they could be liable for the damage.
I do not think there is any health concern as a Sticker product in not used with toxic chemicals.
How do I remove hard water spots on vehicle windows, that have been driven and exposed to all sorts of elements? Besides hard water stains, there are other unknown spots. Thank you.
By Lee 11/13/2010
Vinegar. I use it in my dishwasher and on my stainless steal sink. What a difference!
I have frosted glass by the side of my front door, it is the length of the door. The problem I am having is I can't get the water stains off of it. I've tried several glass cleaners but it always looks the same. Its outside so it gets wet quite often. Is there anything I can use to get those stains off? Please help.
By Dawn from Spokane, WA
By Vi Johnson 04/07/2010
Use the vinegar. I'd use a scrubby sponge though. Then after you get it clean, use a lemon oil furniture polish with a terry wash cloth to apply to the glass where the water hits it. You'll most likely have to re-apply every couple of weeks but it sure helps on our glass shower doors.
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At my model home, the irrigation system sprays the windows and the storm door on the front door. They are all covered with hard water stains. I know Whink will work but I can't find it in my little neck of the woods. What else can I use that won't harm the brass tone trim or the vinyl sash? I have oxy cleaners and The Works. Will either of those work? I have several spec homes with windows that need to be cleaned so I am looking for the quickest and easiest cleaning solution.
Tracy from Twin Cities, MN
How do you remove hard water spots from windows?
Manette from Park City, UT
There have been a lot of great answers for how to clean shower glass, but I'm concerned about how some of these suggested cleaning agents will react with rubber and auto paint. So I want to ask what people have found effective and safe for getting rid of hard water stains on auto glass. Thanks.
Daniel from Ocala, FL
How do I get hard water stains off a window? The sprinklers hit it and there is a mark.
I have water marks on my windows and can't seem to get rid of them. There is also a substance that I think is paint, but I am not sure. I have tried vinegar window cleaners, but with no results. I would appreciate all ideas. I just moved into this house and am a fanatic about clean windows .
Elizabeth from Santiago, Chile