Hi all,
I work in water treatment and have setup over 50 large scale water treatment plants.
I read this page and it seems people here are worried that chlorine can harm your plants.
The answer to this question is based purely on dosages. In high enough dosages chlorine Is toxic to humans, animals, plants and all aquatic life.
Chlorine is also carcinogenic. Chlorination leads to halogenated tri-halomethane disinfection by products, which have been proven to be cancer causing agents. (
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1257669/)
That being said, if your dosage of free chlorine (not actual chlorine) is less than 100ppm then your plants should be more than happy to drink the water.
Chlorine gets "used" up by reacting with organics. If you are growing in soil or coco then that will naturally de-activate the chlorine in the water as the chlorine will try and oxidise or react with the organics in coco / soil etc. This is bad because this reaction will create tri-halomethane by products which are limited to 1ppb due to its carcinogenic properties. I don't think this will harm the plants, but the waste water could allow exposure to a human/animal etc.
As Chlorine is an oxidizer it is possible for cl to oxidise metals into non-dissolvable forms. Making nutrient absorption of manganese and iron impossible.(this holds true for any oxidant aswell) (like ozone).
Cl can also have adverse effects on cation exchange bearing mediums due to its strong oxidisation potential. This holds true for any other oxidants aswell. (like ozone).
If you are growing in pure water, the cl will off-gas fairly quickly into the air. I wouldn't worry too much about it. Most taps are aerated so when you use the water the CL has already been aerated out of the water. This also increases the dissolved oxygen in water as it can take upto 5 days for water from a water treatment plant to reach your home.
Hope that helps