Water is a crucial aspect of hydroponics. Because hydroponic systems do not have soil that can deliver nutrients to the plants, the water must have the nutrients necessary to sustain the plants. Although commercial hydroponic operations can afford to use reverse osmosis and other water treatment techniques that ensure ideal water conditions, many home growers cannot afford such systems.
Can you use tap water for hydroponics? Yes, if you live in an area with safe drinking water, you can use it for hydroponics. However, you may have to treat the water before using it. This may involve adjusting the pH or removing disinfectants such as chlorine.
Although it is generally okay to use tap water for hydroponics, it is important to make sure. This blog post will show you how.
Tap Water vs. Distilled Water
I have read several hydroponics sources that advocate using distilled water. While this is certainly an option, I feel like this is an unnecessary expense for most people. Whether you use distilled water or tap water, you will have to treat the water.
Before I convince you that it is okay to use tap water, it is important to understand the differences between distilled water and tap water.
Tap Water
Tap water is defined as the water that comes out of your faucet or tap. It is typically used for drinking, washing, cooking, showering, and flushing the toilet.
Your tap water will differ depending on where you live. For example, if your water comes from groundwater, it will typically contain more total dissolved solids. If your water comes from a private well, you will not have any issues with chlorine.
Tap water is generally safe to drink if it comes from a public water supply system in the United States. The United States Environmental Protection Agency (EPA) has stringent drinking water standards and enforces those standards. As a result, it is generally okay to use tap water for hydroponics. However, you should do some research and perform a few water quality tests before using tap water for hydroponics.
Distilled Water
In contrast to tap water, distilled water is water that has been boiled into a vapor and condensed back into a liquid. As a result, it does not contain any nutrients, minerals, or metals. It is essentially pure water.
How Tap Water Affects Hydroponics
It is important to keep in mind that the chemical composition of your tap water will vary depending on where you live and where you get your water.
If you want to learn more about what is in your tap water, I recommend looking up your city’s Annual Water Quality Report. The EPA has provided guidance (click here) on how to read and interpret Annual Water Quality Reports.
If your tap water comes from a water well, your city or county’s Annual Water Quality Report will not be applicable to you. The United States government does not regulate private water wells. This means, unfortunately, that homeowners are responsible for testing and maintaining their water wells. Click here for more information on testing your water well.
Chlorine
Chlorine is the most commonly used disinfectant in water treatment. It removes pathogens and provides odor control.
Chlorine can have a toxic effect on beneficial bacteria and single-celled organisms that live on the roots of plants.
Fortunately, it is easy to deal with chlorine in tap water. Simply leave your tap water out in sunlight for a day. Ultraviolet (UV) radiation will break the chlorine down.
Chloramine
Another disinfectant commonly used to treat drinking water is chloramines. “Pool smell” is due to chloramines. Chloramines are commonly formed by adding ammonia to chlorine. They have long-lasting effects and do not break down quickly in water pipes.
Chloramines have been used by municipalities in the United States since the 1930s. According to the EPA, more than one in five Americans consume drinking water treated with chloramines.
Unlike chlorine, chloramines will not easily break down if you leave your water exposed to the air for a day or two. If you want to remove chloramines from your water, I recommend using an active carbon filter like a Brita Filter. You can also use water from your refrigerator. Most built-in refrigerator filters use activated carbon as the filtration medium.
Another option is to use Campden tablets to remove chloramines. This is a common technique that homebrewers use to treat the water they use for beer brewing. Simply add one Campden tablet per 20 gallons of water and let the water sit for 20-30 minutes.
Many sources have recommended using sodium thiosulfate to remove chloramines from your tap water. This is a product commonly used by aquarium owners. However, it is important to note that sodium thiosulfate will only neutralize the chlorine portion of chloramines not the ammonia.
Total Dissolved Solids (TDS)
Another component of tap water that you should be concerned with is total dissolved solids (TDS) which is the total amount of minerals, salts, and metals dissolved in water.
TDS is what people often refer to as “ppm.” Ppm stands for parts per million and is a unit of measurement used to describe the concentration of several substances. It is not correct to refer to a pollutant as ppm.
The only accurate way to measure the TDS in your water is to evaporate the water and weigh the leftover solids. This is not a realistic or productive exercise for home growers. Luckily, you can determine TDS indirectly by measuring the electrical conductivity (EC) of the water. A TDS meter will measure EC and convert that to an estimate of TDS.
By definition, distilled water would have a TDS very close to zero ppm. Tap water will have higher concentrations of TDS. According to the EPA, drinking water should have a TDS concentration less than 500 ppm. Most people recommend using tap water with TDS concentrations between 200 ppm and 400 ppm.
Unfortunately, it is difficult to remove dissolved solids from water. Refrigerator filters and other kitchen filters are not rated for TDS reduction. TDS removal typically requires reverse osmosis or other specialty filters.
pH
Another important aspect of any hydroponics system is the pH of the water in the reservoir.
pH stands for “power of hydrogen” and ranges from 1 to 14. Solutions with a pH under seven are considered acidic, and solutions with a pH above seven are considered basic.
pH is the logarithm of the hydrogen concentration of an aqueous solution as shown below. Concentration is in units of moles per liter.
pH = -log[H+]
Because it is a logarithmic scale, there is actually a big difference between a solution with a pH of 6 and a solution with a pH of 7. A solution with a pH of 6 is 10 times mor acidic than a solution with a pH of 7.
It is important to know the pH of the water in a hydroponics system because it is related to nutrient availability. Typically, nutrients are most available when the pH ranges from 5.5 to 6.5. When the pH is out of this range, the plant will not be able to absorb the nutrients it needs. In addition, other nutrients such as metals can become toxic.
You can measure the pH of your system using a pH meter.
If you find that the pH of your system is outside of this acceptable range, there are product that will adjust the pH of hydroponic nutrient solutions. These products are called pH Up and pH Down.
Adding nutrients to your hydroponic system generally causes the pH to go down (become more acidic) over time. This means it is important to monitor the pH of your system over time.
Hard Water
Have you ever seen mineral buildup on your shower head or faucet? Do you find it difficult to later soap in the shower? If so, you may have hard water. Hard water is characterized by high levels of minerals and salts especially calcium and magnesium. Hard water is also associated with high pH levels.
In order to bring the pH down to an appropriate level, you should add phosphoric acid to neutralize the bicarbonates present in hard water.
In addition, you may consider purchasing nutrient solutions specifically made for hard water.
Conclusion
So can you use tap water for hydroponics? Generally, yes it is. However, you should do some research about the water in your area and do a little testing. You can prepare ideal water conditions relatively easily which will increase the chances of your hydroponic system being successful.