7 is neutral on the p.H. scale. The average p.H. of rain water is around 6.2 on the p.H. scale. If rain water is captured and stored in tanks for drinking then becomes acidic due to a variety of reasons (biology, pollution, tank material, etc…) we can add a bit of limestone (the rock – not the powder) inside the tank to cut and balance the acidity to a more balanced neutral state. It is wise to switch and add small bits of rock slowly as a slightly acidic water lathers and bathes well. The more alkaline the the water the more dry skin and difficulty washing of clothes becomes. *Note this is only used to balance p.H. and not a solution (such as distillation) to take out toxins.
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