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chlorine dissipation

Posted by north53 1b Manitoba (My Page) on
Wed, Jun 20, 12 at 9:41

Is it an old wives tale to allow water to sit to allow chlorine dissipation before watering plants?
I've been doing this faithfully, but just read on another site that's there's no truth in it.
So am I wasting my time? Sometimes our tap water has a strong chlorine odour.

Follow-Up Postings:

RE: chlorine dissipation

Hi North. I can't tell you the number of books I've read advising indoor gardeners to keep water overnight before watering. Especially, Chlorophytum/Spider Plants. Spider plants are sensitive to Chlorine.

I keep old, cleaned milk containers. At one time I had 17, lol. The containers were hidden behind taller plants.

Nowadays, I have 8 containers downstairs and 3 upstairs.

However, plants like soaking in water. Therefore, they're placed in the sink filled w/water until the top soil is wet.
Then sprayed, too..With regular tap.

Whether or not there's truth to it or not, it's something I've been doing over 20-years, and will continue doing so.


RE: chlorine dissipation

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Wed, Jun 20, 12 at 11:37

Copy/pasted from something I left on another thread a while back:

Only in water purification systems that are throwbacks to the 50s & 60s will you find a volatile form of chlorination. This is because of it's short half life. Newer forms of chlorination use chloramine, which doesn't gas off like previously used compounds of chlorine. The fluoridation process (of drinking water) has always used a compound that is nonvolatile, so it too, remains in any water left out to rest - no matter the length of time.

In fact, since evaporation occurs while water is resting (especially if it is in a container that has a lot of air exposure at its opening - like a pan or bucket) the level of chlorine, fluorine, and any other solutes in the water becomes more concentrated as water rests and a fraction of its volume evaporates, leaving the solutes behind.


RE: chlorine dissipation


It isn't that I'm disagreeing with you, :) but I am curious as to what ingredients, 'cotaminants' are in Chicago/Lake MI's water.

I first Googled, but couldn't find much information.
People on a beer-making forum were talking about the amount of chlorine in Chicago's water..they came to the conclusion, water should be boiled.

I then decided to phone City of Chicago Water Dept. It took several calls before talking to someone who knew, (correct phone number) which led from one call to another.

Maybe I'm being a little over-optimistic, but I left a message on their answering machine/voice mail and expecting a return call. lol.

You mentioned, leaving water in an opened container.....
What if the container is capped? Thanks, Toni

RE: chlorine dissipation

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Wed, Jun 20, 12 at 15:08

I just spent about 10 minutes looking around the net. Basically, I came up with the fact that gaseous chlorination is pretty much considered antique, and that was the form of chlorination that WOULD gas off if you left it sit out in an open container, like a pan or bucket. A container with a small opening, like a milk jug would be far slower than a tub, for instance.

This kept coming up at a number of municipal sites that addressed their drinking water:

Chloramine Removal

How can I remove chloramines from my tap water?

Unlike chlorine, chloramine can't be removed from drinking water by boiling water, allowing water to sit at room temperature over an extended period of time or by using reverse osmosis filters. However, there are commercial products available that remove chloramine from drinking water. Please contact a local carrier of home water filters for information on chloramine-removing filters.

Apparently, ascorbic acid (vitamin-C) is effective in neutralizing chloramination, but I didn't chase that too far for lack of time at the moment. If someone wants to look into it, they might be able to do us all some good .....


RE: chlorine dissipation

I contacted our water department about a year or two ago to see if they used chloramines, and the answer was no, just chlorine. I live in a city with a population of 50,000 within a greater metropolitan area of over 3 million, so I wouldn't think our water supply is antiquated, but who knows? I don't know how common it is, but there are definitely areas that do not use chloramines. A quick email to the local water department should give anyone the answer they're looking for.

Also, chloramines are removed by RO filtration. Chlorine and chloramines would quickly destroy an RO membrane, so prefilters are used to remove them before they can reach the membrane. Carbon block prefilters are used to remove chlorine, while granulated carbon filters are used to remove chloramines. If you were concerned about it, you could install filter housings with the appropriate prefilters to easily remove chlorine/chloramine.

That said, I've never had a problem using chlorinated water on my plants. My bigger concern is our alkalinity of 300ppm CaCO3, so I treat my tap water with vinegar and then use immediately.


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