It’s no longer enough to leave your tap water out for day to let the chlorine evaporate, because water is being treated with chloramine, which takes so long to evaporate that other methods of removal or neutralization are needed.
For a lot of reasons, chloramine sanitizes water more effectively than simple chlorine gas. In fact, chloramine’s slow evaporation rate is one of the reasons it’s used instead of chlorine. Taking this into account, gardeners and clean water lovers alike need other methods of removing this noxious compound.
It normally finds itself at around 1-2 ppm in tap water, with the EPA limit set at 4 ppm, meaning a few milligrams of chloramine per liter of water. This small amount, supposedly too small to be toxic to humans, is toxic to aquatic and amphibious organisms, and of course microbes. While the EPA will tell you it’s not bad for plants, scientists haven’t done any major conclusive studies. Some evidence points to chloramine stunting root growth and healthy development; just on principal free-radical oxidizers don’t mix well with life. It certainly will hurt organic growers whose soil relies on beneficial microbes, while Aquaponics (a closed-loop system that uses fish to provide nutrients) is utterly incompatible with any detectable presence of chloramine.
Chloramine is surely quite nasty, but have no fear; a number of ways exist that either completely remove or drastically reduce the amount of chloramine in tap water. The filtration/neutralization method that’s best for you will depend on how much water you need to purify, how close the water source is to your garden and what is most convenient to you as far as time consumption, cost and labor.
When looking into a water filtration system, make sure it carries the National Sanitation Foundation’s NSF Certified logo. You can look up all the filtration systems they’ve certified in their comprehensive, yet confusing, database.
Reverse osmosis (RO) is a great water filtration option for plants and drinking water alike. Leaving water with almost no dissolved solids at all it’s an excellent choice for hydroponic growers. If large amounts of water need to be purified, RO systems can be professionally installed under a sink, or even be made to filter all the water coming into the house. Not only does it remove chloramine and chloramine by-products, it is one of the only methods that also rids water of heavy metals.
Don’t be worried about arousing suspicion; because RO is about the only method that removes fluoride all you have to do is act like an anti-fluoride fanatic.
To work effectively, water going through a RO filter needs to be pre-filtered so the membrane doesn’t get clogged with gunk. A professionally-designed system should include this part, but check, anyway. Also make sure to replace them as often as the manufacturer recommends; an old filter can do more harm than good.
Some of RO’s disadvantages include its electricity and water usage. You only receive around 10% of the water going into a home RO system, the rest gets sent back as wastewater. I recommend reading this document before investing in an RO filter system.
Activated and Catalytic Carbon
An everyday water filter pitcher uses activated carbon to reduce contaminants and make tap water taste better, but to truly remove as much chloramine as possible the water needs to have more contact time in the filter. Catalytic carbon is a souped-up version of activated carbon and is more effective at removing chloramine, even with less contact time. Whole-house activated or catalytic carbon filtration systems can be used, but make sure they carry the NSF Certified logo on them. In order to earn the NSF certification the filter only needs to take chloramine levels from 3 to 0.5 ppm, and any carbon filter isn’t good at removing heavy metals.
If you only need to filter relatively small amounts of water, two filters can be used in tandem to achieve the highest purity. Unlike RO, carbon filters won’t demineralize your water.
The chlorine atom in the chloramine molecule is in an unstable state, making it reactive and dangerous for living organisms. Chloride, on the other hand (as in sodium chloride: regular table salt), is a stable version of the chlorine atom that’s actually necessary for plant growth.
Methods that chemically neutralize chloramine in tap water transform it into chloride and other benign byproducts. Compounds that do this include sodium thiosulfate, Cambden Tablets and, perhaps the most interesting one, ascorbic acid aka vitamin C.
Sodium thiosulfate (typically used for aquariums) and Cambden tablets (mostly used for home brewing) are tried and true at neutralizing chloramine but will invariably increase the TDS measurement of the water by adding sodium and sulfur.
Vitamin C is a fairly new method that works just as well, and won’t add any excess minerals. Just like it’s an antioxidant in the body, it essentially does the same thing for water.
There are shower heads for sale online that claim to eliminate chloramine by using Vitamins C, but don’t be fooled; there’s no evidence to back up the claims. The reaction between ascorbic acid and chloramine takes a minimum of four minutes to go to completion, meaning there’s no way those shower heads do anything at all besides waste your money. You’re better off investing in tablets or purchasing your own food-grade vitamin C if you only need to clean smaller amounts of water.
Ultraviolet light is also good at neutralizing chloramine, as well as killing microbes. It is often used as a pre-filter in RO systems to protect the membrane from chloramine and bacteria.
Make sure to contact your local water supplier for information on your water. Also, consider investing in a chloramine tester to ensure that your filtration/neutralization system works and to figure out when it needs to be replaced or upgraded. Water is always an important thing to consider when growing plants or raising fish, so make sure you know the facts and keep it clean!