How To Treat Tap Water for Hydroponics6 min read

How to Treat Tap Water for Hydroponics 

Tap water might seem like the obvious choice for your hydroponic system – it’s readily available and seemingly clean. However, tap water often contains hidden additives and minerals that can be detrimental to plant health.  Chlorine, used for disinfection, can harm delicate roots and throw off the balance of your nutrient solution.

Minerals found in tap water can also lead to problems. Hard water, with high mineral content, can prevent plants from absorbing essential nutrients. Additionally, the pH level of tap water is often outside the optimal range for hydroponic plants.

Understanding how to treat tap water is crucial for the success of your hydroponic garden.  Let’s dive into the methods for transforming tap water into a perfect growing medium for your plants.


Why Treat Tap Water? 

Let’s break down the specific ways untreated tap water can disrupt the delicate balance of your hydroponic system:

  • Chlorine/Chloramine:  Chlorine and chloramine, used to disinfect municipal water, are essential for safe drinking water but highly damaging to plants.  They disrupt the beneficial bacteria living in and around roots, hindering nutrient uptake and overall plant health. Prolonged exposure can weaken plants significantly and even lead to plant death.
  • Minerals and Hardness:  Tap water, especially in certain regions, can contain high levels of dissolved minerals, making it “hard.” While trace amounts of calcium and magnesium are beneficial, excessive mineral content creates multiple problems:
  • Nutrient Lockout: Excess minerals can bind to the nutrients in your solution, making them unavailable for plants to absorb. This leads to deficiencies, even if your nutrient mix is perfectly formulated.
  • Buildup: Over time, minerals can precipitate and form scale on pumps, tubing, and other components of your hydroponic system, causing clogs, reducing water flow, and potentially damaging equipment.
  • pH:  The pH level is critical for nutrient solubility and availability in hydroponics. Most hydroponic plants thrive in a slightly acidic pH range (5.5-6.5). Tap water is often alkaline (above 7), which can make it difficult for plants to access certain nutrients, leading to deficiencies and stunted growth.


Methods of Treating Tap Water 

Fortunately, there are several ways to transform tap water into a suitable growing medium for your hydroponic plants.  Let’s examine the most common methods, along with their pros and cons:

  • Letting it Sit (Dechlorination):
  • The simplest method is to let tap water sit in an open container for 24-48 hours. This allows volatile chlorine to evaporate naturally.
  • Pros: Free, easy to do, removes chlorine.
  • Cons: Time-consuming, may not remove chloramines (which are often used by municipalities), doesn’t reduce mineral content.
  • Filtration:
  • Reverse osmosis (RO) filters: These highly effective filters force water through a semipermeable membrane, removing a wide range of contaminants including chlorine, chloramines, minerals, salts, and other impurities.
  • Pros: Produces very pure water, removes both chlorine and chloramines.
  • Cons: Expensive, can be slow, wastes a significant amount of water (requires more input water to produce the purified output), removes beneficial minerals along with unwanted ones.
  • Activated carbon filters:  These filters use a porous form of carbon to trap contaminants. They are effective at removing chlorine, chloramines, and some organic impurities.
  • Pros: More affordable than RO systems, removes chlorine and chloramines, improves water taste and odor.
  • Cons: Less effective at removing minerals than RO, filter needs to be replaced regularly.
  • Chemical Treatments
  • Dechlorinators: These products, often found in aquarium supplies, quickly neutralize chlorine and chloramines.
  • Pros: Fast-acting, easy to use, relatively inexpensive.
  • Cons:  May not address hard water issues, requires precise dosing.
  • pH adjusters: After other treatments, you might need to adjust the pH of your water using pH Up or pH Down products, ensuring it falls within the optimal range for your specific plants.


Considerations and Additional Tips 

The most suitable water treatment method for you depends on several factors. Consider these before making a decision:

  • Test Your Water:  Get your tap water tested to understand its specific composition. This will reveal the presence of chlorine vs. chloramine, the hardness level, and the pH.  Many local water utilities provide test results online, or you can purchase a test kit.
  • Cost vs. Convenience:
  • Letting water sit is the most affordable option, but it can be inconvenient if you require large volumes or need water quickly.
  • Filters provide faster results but vary in upfront and ongoing costs (RO is more expensive than activated carbon).
  • System Size & Plant Needs:  A small, simple hydroponic setup might only need a dechlorinator, while a large-scale system with sensitive plants might warrant the investment in a RO filter.

Additional Tips:

  • Water Storage: Store treated water in a clean, sealed container to prevent recontamination.
  • Regular Testing: Even after establishing a treatment routine,  periodically test your water to ensure its quality and adjust your method if needed.

Some things to Consider:

If you are wanting to go all in and build your own hydroponic system for home, but don’t have the time, I want to recommend 2 of our affiliates: Lettuce Grow and Growace:

Lettuce Grow offers an amazing product called the Farm Stand and is beautifully simple. I highly recommend them. They offer financing if you would like that.

Growace offers a complete tent growing kit that is a little more technical but will get you growing in a similar amount of time as Lettuce Grow, about 2 weeks. Check them out, and please consider either one as your new at home system.


Taking the time to properly treat tap water is an essential step in creating a healthy environment for your hydroponic plants. By understanding the potential issues with untreated water and the different treatment options available, you can choose the method that best suits your needs and budget. Invest in water treatment and watch your hydroponic garden flourish!

Additional Notes:

  • Start by testing your tap water to determine its specific qualities. You may be able to find a water quality report online from your local utility, or you can purchase a test kit.
  • Visit a local hydroponics store for personalized advice and to explore different treatment equipment options.
  • Connect with the online hydroponics community! There are numerous forums and resources where you can ask questions, share experiences, and continue learning about this exciting method of growing.



  • Q: Can I use rainwater for my hydroponic system?
  • A: Rainwater can be a good option, but it’s important to test it first. Rainwater can be slightly acidic and may contain contaminants from air pollution, especially in urban areas.
  • Q: Is bottled water safe for hydroponics?
  • A: While generally free of chlorine and chloramines, bottled water can vary in mineral content and pH. “Spring water” may still have a high mineral content, while distilled or purified water lacks beneficial minerals.  It’s best to test bottled water before relying on it for your hydroponics system.
  • Q: How often should I change the water in my hydroponic system?
  • A:  This depends on your system size, plant types, and nutrient solution. A typical recommendation is to change the reservoir water every 1-2 weeks, but you may need to do it more frequently with faster-growing plants or a smaller reservoir.
  • Q:  My water is very hard; what’s the best treatment option?
  • A:  If you have hard water, a reverse osmosis (RO) filter is the most effective way to remove excess minerals. You may also consider diluting your tap water with RO or distilled water to reduce the mineral concentration.
  • Q: Do I need to treat my water if I’m using well water?
  • A: Absolutely! Well water can contain significant minerals, iron, or other contaminants that can harm your plants. Get your well water thoroughly tested to determine the best treatment approach.



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