Answer: Leaving the water out over night would allow time for chlorine (such as is added by a municipal water company) to evaporate from it. It would not change the lime content. If you have a problem with hard water or are worried about changing the pH of your soil due to alkaline water, you could water with saved rain water instead. Do not use water that has been through a water softener to water your plants, it will contain damaging salts. I hope this answers your question.
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