Hard water is caused by an excess of minerals, usually magnesium and calcium, in the water. The presence of these minerals not only adversely affects the taste of the water, but it also poses several problems when it comes to laundry. Hard water can cause clothes to appear dingy and yellow, make them more prone to soil build-up, feel stiff and rough, as well as cause white or gray streaks on colored fabrics. Hard water stains can be removed from clothing, white cotton included, by using the right detergents and a little extra effort.
Fill your washing machine with hot water. The hotter, the better. Hot water is typically safe for cotton clothes, though you may wish to check the tag for specific warnings regarding temperature.
Measure out four times the usual amount of a phosphate-based powdered detergent and add it to the hot water. It is important that you use a phosphate detergent because non-phosphate detergents negatively react with hard water and can result in leaving your clothes feeling stiff.
Add 1 cup of water conditioner to the washer. Water conditioner helps balance the chemical makeup of the water. It can be purchased at most department, grocery and/or hardware stores.
Place your white cotton clothes into the washer and agitate them for a short period of time. Make sure the clothes are thoroughly wet and then stop the cycle before it continues.
Allow the clothes to soak for approximately 12 hours and then drain the water from the washer. Set the machine to a spin cycle in order to remove any excess water.
Wash the load as you normally would using a regular cycle. Do not add any detergent. Only use another cup of water conditioner.
Wash again with water conditioner, if necessary, until all soap suds disappear during the rinse cycle. If stains are still noticeable, run through the washer one more time using a cup of water conditioner and bleach. Use the amount of bleach recommended on the container that is specific to the size of your load of laundry.
If you are experiencing persistent problems with hard water, check into purchasing a water softening system that can be hooked directly to your water supply lines. If your clothing is stained with what appears to be rust, this is caused by an excess of iron in the water. Technically, this is not hard water. Attempt to remove these stains by sprinkling salt onto the stain and moistening it with lemon juice. Dry the clothing in the sun and rinse.