There are a number of commercial acid-based cleaners available from masonry dealers or "big box" home stores. Follow the directions carefully.
Consider the application of something like silane- or siloxane-based sealer. Check it out when you go look at the cleaners.
Another safer way would be to use a mild acid solution first such as white vinegar. This has been proven to work and is not toxic. See below for step by step guide...
Natural Formula to Use:
½ liter white vinegar and ¼ liter of water
Method to Use:
1.Fill a clean spray bottle with pure vinegar
2.Spray the vinegar/water solution over the brick and wait for a few minutes
3.If stains are stubborn spray more solution and wait a while longer
4.Scrub lightly with a stiff brush and rinse
Tip:
Try to deal with the water spots straight away as the solution works best with newly formed or mild hard water spots. It is also a good idea to use gloves to prevent the strong smell of vinegar staining your hands and clothing.
for a brick to float on water 2 thirds of the mixture should be salt
You will need to use a sealant, such as Killz, to keep the stains from bleeding through the new paint.
Water.
Neither white vinegar nor water stains clothes. Red wine vinegar may though, as it is made red wine which stains.
A quick sweeping or vacuuming removes dirt and debris before it can become embedded in the tile or grout. Mopping with warm water and using a manufacturer-recommended cleaning product also enhances your tile's gloss, shine, and color. You can also mix hydrogen peroxide and water in equal parts. Simply apply this with a toothbrush to remove the stains. You will find that even grout that is properly maintained is easier to clean and remove stains from than other surfaces, such as laminate.
Diluted bleach can clean stone brick stucco. Often gentle water pressure can remove hard water stains on stucco as well.
Scrub it down with fresh water and a stiff broom or brush
water
Wet the stain with water and apply Bar-Keepers Friend.
water
To remove coconut water stains, first soak with cold water for a small amount of time. Then, spray the stain with a stain treatment, then wash in cold water.
Oil and grease stains are tough to remove from clothes because they resist water. The water in a washing machine works around the stain. Detergent makes it possible to remove oil and grease stains.
Vinegar.
Pledge will remove water stains from wood as well as apply a protective layer to help keep new stains from forming.
i suppose your wa shing machine leaves stains as well
You can use a solution of two parts water to one part white vinegar to remove water stains from glassware.
Kaboom! Kaboom!