Question
hi
i was wondering if i need to leave my water set out overnight before i use it to water my plants? i live in the city       thank-you Kim

Answer
Hi Kim,

There is much confusion about this issue. The practice of letting tap water stand in an open container overnight is based on the idea that chlorine and fluoride in water dissipate (evaporate) into the air and out of the water so it cannot harm potted plants. While it is true that chlorine in water supplies will dissipate into the air, fluoride does not. The concentration of chlorine in city tap water is not usually high enough to damage plants. Chlorine levels in swimming pools is high enough to cause plant damage, but presumably you are not using swimming pool water for your potted plants!

The primary problem with using tap water is that in many areas the tap water is hard, meaning it has a high mineral content. These minerals can be damaging to plants over an extended period of time. Unfortunately, these minerals do not dissipate into the air so leaving the water in an open container over night does not solve the problem.

The bottom line is that unless your local tap water is on the hard side there is no reason to let the water stand overnight. If your tap water is hard, then switch to filtered, distilled or rainwater for use on your plants.

Please let me know if any of this is unclear or if you have any additional questions.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

Visit my website at: A link to HorticulturalHelp.com