If you take a soak in a bathtub filled with hard water, you'll wind up with dry, itchy skin. The best approach to correcting this situation is to install a water softening system, but there is an effective quick fix. This technique comes in handy if you're staying with a friend, relative or hotel that you've visited before and that you know has hard water.
Run the bathwater and adjust the balance between hot and cold until the water is pouring at a temperature that suits you. Put the plug into the drain and allow the tub to fill.
When the tub is approximately three fourths full, turn off the water.
Measure out a half-cup of baking soda using a measuring cup. Pour the baking soda into the tub.
Stir the tub water around with your hand until the baking soda is evenly distributed and mostly dissolved.
Bathe as usual. When you're done, empty the tub as you usually would.
Hard water damages and dries out the skin because it is saturated with calcium and magnesium deposits. Baking soda counteracts the moisture absorbing power of these mineral deposits. If your skin is very sensitive to hard water, take a box of baking soda with you when you travel or make plans to buy some when you reach your destination. It's generally best for the most sensitive-skinned people to assume that a home or hotel has hard water than to take the chance.