The hardness of your tap water has an effect on the efficiency of soap, shampoo, laundry detergent, dish soap, etc. — including your no-poo method. The harder the water, the more minerals the water contains– and the harder it is for soap to lather and clean. In hard water, more soap is needed to do the same job that less soap could do in softer water.
What it feels like: Soft water feels slippery when you wash your hair. Soap lathers easily and washes out easily. It’s the opposite in hard water. Hard water is more alkaline which causes the ridges on our hair shafts to stand up. The minerals in hard water get stuck on the rough edges of our hair strands, causing hair to feel tangly, dry, and unmanageable, feel like there is buildup on hair, cause color dye to wash out, and even cause dandruff.
To determine the hardness of your water, you can test it at home, but you should also look it up on your city’s website (Example 1)(Example 2) to see where your water falls on the hardness range. You can also ask your homeowner whether or not your home contains a water softening system (which would then mean you have softened water).
There are some inexpensive options you can use to soften your water. For hair washing, the two common solutions are to use distilled water (or boil your own water to remove some of the impurities – instructions here), or to install a shower head filter. Many people in this community have had success with a shower head filter.
Note: Bottled water doesn’t mean softened water and many times it’s no different from tap water, and drinking water filters don’t always remove hard minerals, so research these brands before buying and using.