A Guide for Using Tap Water in Your Garden

girl-watering-her-gardenI understand the frustration that gardeners experience when they are forced to use tap water for gardening purposes. For most of my gardening life, I have been on municipal water. It is true that plants don’t seem to like it. However, when I moved to a residence that had well water, I did not notice any difference in my garden.

Most gardeners have noticed that plants love rainwater. But we have to ask, are the plants responding to the water, or are they responding to the rainstorm? Rainstorms add nitrogen and energy to water before dropping it on our gardens. Maybe that added nitrogen and energy is the reason we see our plants spring up after a good rain. It might not be about the absence of chemicals, it might be about the presence of natural energy from the storm.

We can find ways to improve tap water to make it safer for our gardens. But can we replicate the magic of naturally healed water, with nitrogen and healing energy? That’s a tall order! Let’s look at all of our options, because when rainwater is not available many of us are stuck with the damaged, chemical-laden water that flows from the tap.

The Chemicals Used to Treat Tap Water

Let’s address the chemicals first. While old-fashioned chlorine can be dissipated out of water with air contact, the process of doing so is burdensome for the average gardener. To make matters worse, in recent years many water treatment facilities have switched to chloramines rather than chlorine. What are chloramines, you ask? When water is treated with both chlorine and ammonia the chlorine is converted to chloramines, in a process known as chloramination. This process came into use because when chlorine alone is used for disinfection, small amounts of plant material that are carried in the water can create unpleasant flavors and odors. This occurs because of the phenols present in the plant material. When chlorine is introduced, rather than going away these phenols bond with the chlorine to produce chlorophenols.

So the change to chloramines was really done to eliminate the foul taste and odor of chlorophenols. If chlorine could be converted to a less active form after being used to disinfect water in a treatment plant, then it could still retain some of its disinfecting power, without being strong enough to form chlorophenols during its trip through the water mains. And the customer would not experience the off taste and odor of chlorophenols. This is where the ammonia came in, and chloramines were born in our water supply.

Chlorine also has reactions with other organics found in surface water that are introduced by decaying vegetation. These decay products, mostly humic and fulvic acids, combine with chlorine to produce a family of chemicals known as THMs (trihalomethanes). THMs are widely thought to be carcinogenic. Today’s federal and state drinking water regulations strictly dictate the allowable concentrations of THMs. As a result of this, many more water authorities have switched to chloramination in recent years.

How Tap Water Effects Your Garden

Research studies have shown that when you irrigate your garden with tap water, the damage done to microorganisms in the soil is minimal and temporary. One reason chlorinated water has little impact is that chlorine binds to soil particle surfaces. This immobilizes chlorine and reduces its ability to kill microorganisms. The organisms in the top surface of soil or compost may be affected after irrigation, but as the water moves downward little chlorine remains.

In one study, researchers found that water chlorinated at 5 parts per million killed organisms only in the top 1/2 inch of soil. Organisms deeper than 1/2 inch were still thriving. Note that 5 ppm is much stronger than tap water. In order to kill soil microorganisms to a soil depth of 6 inches, water containing 65 ppm chlorine was required in one study. Tap water usually contains a much lower concentration of chlorine.

The study that came to these conclusions used poor sandy soil with no added organic material other than minimal grass clippings, because they were trying to replicate home lawn care conditions. These soil conditions would not have the level of microbial activity that an organic vegetable garden would enjoy. I have not yet been able to determine how long it takes for the microbial communities to regenerate. “Rapid” could mean an hour, or a day, or longer. During a very hot and dry summer when we might water every one or two days, the degradation rate and regeneration rate would be important!

Finally it is important to note that it is the microbes in the soil that break down the chlorine and the ammonia. The more life that is in the soil, the more quickly the unwanted chemicals will clear up. This shows that keeping your soil rich and full of organic matter is very important if you must use tap water to irrigate. So now let’s look at just how practical the removal of chloramines really is.

Removing Chlorine with Chemicals

In the water industry, the most common methods of dechlorination are the addition of “reducing agents” such as hydrogen peroxide and ascorbic acid (vitamin C). Some water treatment facilities use other chemicals such as sulfites and even additional chlorine. Most of these techniques are not practical for most gardeners, but let’s evaluate H2O2, hydrogen peroxide.

Hydrogen peroxide is a powerful oxidizer. It is also versatile. The fact that hydrogen peroxide is used for seemingly contradictory applications proves its versatility. For example, it can be used to inhibit microbial growth, as in the bio-fouling of water circuits; and it can be used to encourage microbial growth, as in the bioremediation of contaminated ground waters and soils. It can treat easily oxidized pollutants like iron and sulfides, and difficult-to-oxidize pollutants like solvents, gasoline and pesticides. The reason hydrogen peroxide can be used for such diverse applications is that there are different ways in which its power can be directed; this is called selectivity. By simply adjusting the conditions of the reaction, such as pH, temperature, or dosage, a variety of results can be achieved.

For backyard gardening purposes, a simple chlorine test demonstrates the rapid destruction of free available chlorine by hydrogen peroxide. The correct amount of hydrogen peroxide to use is approximately one or two drops per gallon, using a 3% hydrogen peroxide solution available in drug stores. The free chlorine will have disappeared by the time you have finished stirring the water. The presence of excess hydrogen peroxide used in this test is not harmful to soil life, so exact amounts and exact pH of the water should not be important.

What about the use of ascorbic acid? This formula is from a municipal water department: “1000 mg of vitamin C tablets purchased from a grocery store, crushed and mixed with bath water remove chloramine completely in a medium size bathtub without significantly depressing pH.” There are shower attachments available which use ascorbic acid to remove chloramine. One of these attachments could be attached to a garden hose with a simple adapter. The duration of effective chloramine removal may be shorter than the product claims, so it might be a good idea to periodically test the treated water using a chlorine test strip from a hardware store or a pool supply. In my experience, in-line filters and attachments are best attached at the source end of the hose, not at the end you hold. These parts are bulky and they can make it harder for you to water your garden.

Removing Chlorine with Filters

Home chlorine removal systems mostly use activated carbon filters. These filters and their systems vary widely in size and price. The small ones are designed for showers or drinking water, and many of these would be easily adaptable to a garden hose. The inherent problem with the small filters is their correspondingly low flow rate. Most drinking water filters are designed to function with a low volume flow rate. Shower filters are notorious for reducing, not eliminating, the chemicals they are designed to filter. There is one filter I have used that removes chlorine to undetectable levels and has a good flow rate. The Omica shower filter uses some very cutting edge technologies and has good coverage of other water toxins as well. It is easy to find these on the internet.

Depending on the size of your garden, an inexpensive whole house filter may be of interest to you. I have been looking at water filtration systems for a long time and I recently found a two stage system for about $300. The two stage system saves on filter replacement, because the sediment filter prevents the carbon filter from blocking up too quickly.

There is a new technology that is already being used in 120 countries for a broad variety of applications, called EM.  EM stands for Effective Microorganisms, and the technology was developed by a university professor in the early 1980’s. EM ceramics can be used with drinking water to remove chlorine, control odors, make water more hydrating for plants and animals, and to improve water for homeopathic use. The 35 mm pipes are used in a bath or shower to improve cleansing and reduce soap consumption. The pipes can also be used on the water you will use to water your plants. One pipe will remove all chlorine from 55 gallons of water in 30 minutes. Several pipes can be placed inside a water line to create your own water structuring unit to improve the water and reduce chlorine. The pipes do not wear out or get used up, but they do need to be cleaned and recharged with microbes every 6 months.

Chlorine and chloramines are just one part of the many issues we need to understand in order to have good, clean water. We are working on several more articles regarding your water, so stay tuned to learn more.

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