I have offered this solution before: buy a gallon of distilled water, put the distilled water in your soaking cup to what level is normal for you,
put the cup in the microwave on high for a minuet, soak your brush in the hot cup until you are ready to lather then later. If more water is
needed dip the brush back into the cup of distilled water. By doing this you have sidestepped the hard water issue.