Remineralizing RO Water for Plants – What You Need to Know

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While we can cover our mineral intake with the food we eat, plants rely on water for their essential minerals.

RO filtration removes most minerals from water, which means that if you’re using it for your plants, you need to get the minerals back in to help your plants flourish.

Remineralizing RO water – how do you actually do that? Let’s find out!

Key Takeaways

  • RO water should be remineralized when you water your plants.
  • What you use to remineralize/fertilize your houseplants should depend on their own individual needs, but a good thing to start with would be an NPK fertilizer.
  • Also consider adding calcium, magnesium, and sulfur. Required trace elements may include iron, manganese, copper, zinc, molybdenum, and boron.

Remineralizing RO Water for Plants

Plants need around 20 essential minerals in order to survive, and they include potassium, phosphorus, nitrogen, magnesium, and calcium.

Reverse osmosis systems are very effective at filtering these out along with the harmful contaminants. So, you need to make sure your plant soil or water has these nutrients added using a feed product or fertilizer.

Ideally, the kind you use will depend on the plants you are growing. For regular houseplants, recommended fertilizers and feed products include NPK (nitrogen (N), phosphorus (P), potassium (K)) fertilizers with a base ratio of 4:4:4. You can adjust the dose if your plants are heavy feeders or add extra nutrients, like nitrogen for your leafy green houseplants, should it be required.

Other major elements required by plants are calcium, magnesium, and sulfur.

Trace elements include iron, manganese, copper, zinc, molybdenum, and boron.

Again, how much of each you will need to add to your RO water for remineralization varies from plant type to plant type.

watering plants

What’s RO Water (Purification)?

Reverse osmosis water is purified water that has been filtered through a reverse osmosis system. This process uses several filtration steps to rid the water of any impurities and nasty contaminants such as bacteria, viruses, sediment, chlorine, lead, and arsenic.

The semipermeable membrane in a reverse osmosis system has tiny pores that allow small water molecules to pass but will stop any larger ones from getting through. This leaves you with purified water, which means water that is mostly H2O.

Do Plants Flourish on Reverse Osmosis Water?

Providing you are remineralizing the soil or water after it has passed through the RO system, then yes, your plants should flourish on reverse osmosis water.

If, however, you do not remineralize the water, then your plants will not be receiving the essential nutrients they need, and they will possibly die.


While chlorine in municipal tap water supplies is considered at safe levels for drinking, it can be harsh on sensitive plants such as dracaenas, spider plants, and carnivorous plants.

Water pH

Water pH can affect nutrition in the soil and roots of the plant. Ideally, your houseplants need water with a pH of around 6, so slightly acidic.

Good news: RO water usually comes out at around 6.0-6.5, which is ideal.

Sometimes it does drop lower, to about 5.5, which is not considered too much of a problem as it’s not drastically out of the optimal range.

If the pH of your water is really out of whack, it can lead to various issues, such as stunted growth, necrosis, leaf death, and brown spots.


As RO water is free of minerals (the good and the bad), you need to add those back in. Plants deficient in potassium may result in yellow leaves, and nitrogen deficiency will cause the leaves to become stunted and small.

Remineralization can be done with fertilizer salts. Some recommend occasionally mixing your RO water with a bit of tap water to ensure your plants are getting the minerals found in tap water, but not substantial doses of the contaminants.

Advantages and Disadvantages of Using RO Water for Household Plants

  • Removes most contaminants – provides clean water that is free of impurities that can harm your plants, such as herbicides, insecticides, chlorine, and heavy metals.
  • Protects you from contaminants – If you are growing edible plants, RO water will prevent your plants from uptaking lead and arsenic, which can be toxic when ingested.
  • Improves plant growth – The lack of dissolved solids in RO water means they will not overwhelm your plant and cause stunted growth.
  • Complete control of water quality – RO water provides a neutral base for you to remineralize it, allowing you full control of what is going into your plants.
  • Removes beneficial minerals – calcium, magnesium, nitrogen, potassium, and phosphorous are all removed, which are essential for proper plant growth.
  • Acidic water – Sometimes RO creates water that is slightly more acidic than ideal, which could affect the pH of the plant soil and make it hard for the plant to absorb nutrients.
  • Cost and maintenance – RO systems come with higher initial start-up costs and must be maintained. Definitely a more significant expense than tap water.

If you have any questions about remineralizing RO water for plants please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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Leave a Comment:

Becky fredsberg says July 15, 2023

My lawn is not looking as good as I think it should – I have been watering – but am wondering if this may be because our town has reverse osmosis water ….

    Gene says July 17, 2023

    Hi Becky, even if they’d use RO for treatment, they would add minerals back into the water, because otherwise the entire distribution system would corrode.
    If you’d still like to make sure, test your water with a TDS meter!

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