How Do I Choose the Best Soap for Hard Water?

Soaps can build up on the skin when washed with hard water.
Body washes are often a good option for people with hard water.
A bar of soap.
Castile soap will soften hard water and can have a high concentration of coconut oil.
Soaps for hard water are specially formulated to lather and rinse well.
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  • Written By: Elizabeth West
  • Edited By: Shereen Skola
  • Last Modified Date: 08 September 2014
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A soap for hard water is specially formulated to lather and rinse well despite the minerals it contains. Detergents and additives exchange calcium and manganese ions in the soap the same as a water softener would, or prevent them from binding in the first place. Body washes, shampoos and laundry boosters all help, but using a water softener unit is the easiest way to reduce hard water buildup when washing yourself or your clothing.

Hard water comes from aquifers deep beneath the surface where it has long exposure to minerals such as manganese, calcium and limestone. These substances dissolve ions into the water that are suspended in a solution. While not harmful, they leave a deposit on bathroom fixtures, skin and hair. When it comes in contact with soap, the result is a sticky, hard-to-remove film.

Soap doesn’t lather well in hard water because the minerals bind with its elements. This keeps it from foaming properly, which many people feel is essential to removing body oils, dirt and grease. A soap for hard water contains additives that are designed to soften the water as they come in contact with it, thus improving lather and eliminating the film. One of the best varieties is called a castile soap, a mild formula with a high concentration of coconut or other oils.


Manufactured body washes are usually made with detergents that don’t bind with mineral ions as well as the sodium stearate in traditional bar soaps. Body washes come in many popular colors and scents, making them an appealing soap for use when bathing in hard water. They also frequently include moisturizers that remain behind after rinsing and soften skin. While a bit more expensive than bar soap, they are a good choice if you can’t install a water softener, such as in a rental unit.

Clarifying shampoos, designed to remove buildup, are typically the best soap for hard water to use on hair. They usually contain ingredients that strip substances from the cuticle. Clarifying shampoos work not just on hard water buildup but also that left by products such as hairspray that capture mineral deposits and make hair appear dull. The ingredient ethylenediaminetetraacetic acid (EDTA) binds to minerals and removes them before they can be deposited. EDTA breaks down to an environmental pollutant, however, so products with Ethylenediamine-N,N'-disuccinic acid (EDDS) offer a more biodegradable alternative.

Water softeners exchange the mineral ions in hard water with sodium or potassium ions. This eliminates the deposits on clothing, skin and fixtures that bond with soap to make scum. They require adding sodium periodically to recharge them. A softener unit will add sodium to the water in your home, so if you or anyone in your house are on a low-sodium diet this may not be the best alternative. If a softener unit isn’t economically feasible for your household, you can simply add packaged water softeners like borax to laundry to help get clothes cleaner and continue to use a specialty soap for hard water to shower and bathe.


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