Learn what you should know about using chlorinated water in your garden – and ways to remove it for healthier organic soil…
As you learn more about building healthy soil and how important soil microbes are for plant health, many gardeners wonder: Is it okay to use chlorinated water in your garden?
Depending on who you ask, the answers you get may vary. Some studies have found that chlorine at the levels typically found in tap water is not harmful to plant growth, and other studies have shown that it may have only minimal effect on soil microbes near the surface of the soil.
However, some organic gardeners prefer not to take the risk, especially since many controlled experiments may not necessarily reflect the conditions in a backyard organic garden, and may not consider the overall effect this can have on your local soil ecosystem.
As this article points out:
Even if chlorine only kills sensitive microbes or microbes in the upper portion of soil, the loss of those microbes may be significant to the overall health of the soil ecosystem. By this logic, why worry about running over nails and metal debris in your car? All that will happen is that some of your tires will go flat, and tires are only a small part of the car. With potentially billions of organisms per handful of living soil and countless interdependent biological processes occurring continually, the functioning of healthy soil is orders of magnitude more complex than the mechanical operation of a car. Wiping out the top inch or two of soil microbes with chlorinated water could mean killing trillions of organisms in a home garden. The vast majority of soil microbes are directly or indirectly helpful to plants.
Many variables that might be important to understanding chlorine’s effect on soil life have been ignored or not adequately addressed in the research that I’ve seen. A few of these include possible sensitivity or varying effects of chlorine on numerous strains and species of soil microbes, temperature, soil composition, soil texture, and even frequency of soil saturation with chlorinated water.
The bottom line is, if you are growing in basically “dead” soil using chemical fertilizers, chlorine at the levels that are typical in municipal water probably won’t make much difference to your plant health and yield. However, if you are an organic gardener who wants to preserve your soil web and improve your soil health over time, you may want to consider avoiding the use of chlorinated water in your garden.
So how do you water the garden if your local tap water is chlorinated? You have a few different options.
Our preferred method is to water using rainwater. We have routed our downspouts from our barn roof to drain into a fairly large tank (close to 500 gallons), which we use to water the garden. The main downside to this, of course, is that it may run dry during a particularly long dry spell. Fortunately, this hasn’t happened more than a few times over the past 5 years since we started collecting rainwater.
Secondly, you won’t have great water pressure unless you can elevate your tank above the garden level, or use a pump. (We have elevated our tank a few feet, and it usually works fine for drip irrigation until the water level gets fairly low.) The larger the tank, the better the water pressure, and the more water you can collect. We hope to get a larger or a second tank for our garden at some point.
Here are 2 other options that may work, depending on the size of your garden:
Chlorine naturally offgasses from standing water in about 24 to 48 hours. For a small garden or group of potted plants it’s reasonable to leave water sitting in buckets, plastic trash cans, or similar large containers for a day or two before use. I have found this method to be helpful over years for hand watering using a watering can, and it can be efficient when containers are large enough for a watering can to be partly submerged and filled quickly, which I find to be much faster and easier than filling from a hose. Keep the containers near the areas that need to be watered. With enough large containers and a hose running at the right flow, you can be refilling containers for tomorrow or the next day as you water plants by hand from containers that were filled a day or two ago. Without larger tanks and and a more-elaborate delivery system than most gardeners will want to construct, this method is awkward for watering anything but a small garden, and water must be used up or emptied within a few days to avoid creating a breeding ground for mosquitoes.
For larger gardens and landscape areas, hose filters provide a reasonable solution for removing most chlorine. Hose filters are relatively easy to install. They may restrict water flow, and/or filtering performance may be reduced at high water flow. GardenZeus recommends this basic and inexpensive filter, or this better-quality chlorine filter that accommodates a higher flow volume with infrequent or annual filter replacement. Larger entire-landscape or household filters are also available that require installation by a professional.