Hard Water vs. Soft Water: A Hydroponic Guide to Optimal Hydration

Growee - Hard Water vs. Soft Water_ A Hydroponic Guide to Optimal Hydration

People wonder whether it’s soft water or hard water that’s best used for watering plants in a hydroponic setup, and that’s exactly what we are here to figure out today. The fact is that hard and soft water both have their pros and cons that are worth talking about. In some ways, hard water can be good for hydroponics, whereas in other cases, soft water may be better. Let’s determine whether it’s hard or soft water that you need for your hydroponic system.

What is Hard Water?

Hard water is full of dissolved minerals like calcium and magnesium. It picks these minerals up as it moves through rocks, soil, and other sources of mineral deposits. 

Water hardness is measured by examining how much of both of these minerals is present in the water, usually in parts per million. 

There are some parts of the world that have harder water than others. In your hydroponic system, hard water can lead to scale buildups, plus it may cause some issues for your plants as well.

Pros of hard Water

There are a few aspects of hard water that may be good for your hydroponic system, so let’s see what these might be.

  •   Magnesium and calcium are both important nutrients for plant growth.
  •   Hard water has other minerals in it that are good for plants, such as iron and manganese.
  •   Hard water with lots of minerals can make acidic soil more basic, which can be a good thing.
  •   Because hard water contains minerals, it means you’ll need to supplement your plants less.

Cons of Hard Water

  •   Hard water can change pH levels, sometimes for the worse.
  •   High amounts of calcium and other elements can prevent your plants from taking in vital nutrients.
  •   Hard water may contain elevated levels of nutrients and chlorides, which can be detrimental to plants, particularly in a recirculating hydroponics system. When topping off with hard water, the concentration of these minerals can progressively increase, potentially impacting plant health.

Hard Water is Best for Plants That Can Handle Extra Minerals

It’s no secret that hard water is full of minerals that can cause soil and hydroponics systems alike to become more alkaline, which is totally fine if you are using water that starts off as being quite acidic. Moreover, it’s also a good idea to use hard water in hydroponics if you don’t plan on supplementing with too much extra magnesium or calcium.

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What is Soft Water?

If hard water contains a lot of dissolved minerals, then soft water is the opposite. Soft water doesn’t contain many minerals like calcium or magnesium at all. This is just a natural occurrence in many places of the world, or it may be a result of water softeners being used.

Pros of Soft Water

Soft water has beneficial aspects to it just like hard water does, so let’s see what these might be.

  •   Due to having fewer minerals, soft water also does not lead to higher salt levels in your hydroponic system.
  •   Soft water is good to use for hydroponics systems where you are already giving your plants plenty of supplements and nutrients. It will prevent nutrient overload from occurring.
  •   Soft water might also allow Medical plants to more easily absorb nutrients.

Cons of Soft Water

Soft water has drawbacks for hydroponics operations that need to be discussed as well.

  •   Lack of Essential Micronutrients: Soft water typically lacks certain micronutrients vital for plant growth. Growers must compensate by adding these missing elements to ensure optimal plant health.
  • Instability in pH Levels: The absence of bicarbonates in soft water can lead to less stable pH levels, especially problematic when adding nutrients or in recirculating hydroponic systems like RDWC, DWC, and NFT.
  • Increased Maintenance Costs: Using soft water in hydroponics often necessitates additional investment in water treatment and nutrient supplementation. This extra step can increase the overall maintenance cost and effort for the grower.

Soft Water is Ideal for Growers Seeking Complete Control Over Plant Nutrition, Including Micronutrient Levels

Soft water is best for hydroponic growers who want full control over their plants’ nutrition. It’s like a clean slate, free of extra minerals, allowing precise addition of both macro and micro-nutrients for tailored plant growth.

Differences Between Soft Water and hard Water for Hydroponic Growth

Differences Between Soft Water and hard Water for Hydroponic Growth

Now that we know what makes soft and hard water similar, let’s see what makes them different from each other.

  •   Hard water is full of dissolved minerals and soft water is not.
  •   Hard water can cause scale buildups, and soft water does not.
  •   Soft water requires supplementation to add minerals, whereas hard water requires special techniques to remove those same minerals.
  •   Hard water makes hydroponic systems more basic in nature, and soft water does the exact opposite.

·   Hard water can be effectively diluted with an RO (Reverse Osmosis) system. Mixing hard water with RO-treated water will also reduce the water’s EC (Electrical Conductivity) levels

Hard or Soft Water for Plants: Which One Should You Choose?

Whether you use soft or hard water to grow your plants is a question and depends on various factors. Plants that don’t require additional nutrient supplementation will do fine with soft water.

But, if you need the water to be a bit more basic, and your plants could do with some added trade minerals, then using hard water is likely best.

pH Balance with Growee in Soft Water

Soft water often has unstable pH levels, making it challenging for hydroponics. The Growee pH controller simplifies this by automatically adjusting the pH. This ensures optimal conditions for plant growth, overcoming the common pH fluctuations in soft water with ease and precision

Automatically Adding Micro-Elements with Growee Dosing Control

Soft water lacks essential micro-elements and nutrients for hydroponics. Growee’s nutrient dosing control precisely adds what’s missing, ensuring plants get exactly what they need. This smart solution simplifies the process of balancing nutrient levels in soft water, promoting healthier plant growth

Final Words

If you don’t want to have to deal with nutrient and pH monitoring, check out this fully functional Growee Pro Combo that automatically doses your plants with nutrients while consistently maintaining accurate pH levels.

Hard and soft water are both types of water that can in some cases be used for hydroponic grow operations. As long as you keep track of important factors like acidity and pH levels, it should be just fine.  If you’re worried about pH levels, try using this Smart pH Balancer!


It is okay to use for hydroponics as long as your plants don’t get too much calcium and magnesium.

It is okay to use for hydroponics as long as your plants don’t get too much calcium and magnesium.

Hard water usually has a pH of around 7.5 to 8.5 and soft water 6.5 to 7.5.

Hard water will raise the pH level because of the added minerals.

Whether hard or soft water is better for hydroponics depends on the initial situation. One or the other may be better depending on specific circumstances.

As long as you give your plants extra minerals and make sure the conditions aren’t too acidic, then soft water is totally fine.

Hard water is also not bad for your plants, as long as you don’t give them too many extra minerals on the side.

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About Growee

Our goal at Growee is to simplify and smarten urban farming. Our product line is tailored for small-scale growers, and we’re proud to support home growers and commercial growers in over 30 countries worldwide.

The company was founded by a group of engineers and hydroponics enthusiasts and has gained recognition for its innovative technology, including several awards from the Israeli Innovation Authority.

Small-scale growers face the time-consuming task of manual water monitoring and adjustment. Growee’s automated hydroponics system simplifies this process, enhancing efficiency and increasing hydroponic yield

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