Can You Water Houseplants With Softened Water?

Many households have a water softening system to eliminate harsh minerals in their water. These systems are designed to make water safer to drink, flow better through home plumbing, and for activities such as showering and laundry. But it’s it safe to use on houseplants? 

While watering occasionally with softened water won’t have too many adverse effects, watering houseplants with softened water over extended periods can harm your plants. In order to remove the mineral hardness of hard water, the softening process uses salt or chemicals. These build up on the soil and negatively impact growth, potentially leading to the death of your plants. 

This article will explain what softened water is, how it affects houseplants, what to do when salt builds up in your soil, and how to water your houseplants safely.

What Is Softened Water?

Water softening involves breaking down and removing excess minerals in hard water, making it healthier to consume and use in residential, commercial, and industrial buildings. 

When it rains, water flows through the soil, limestone deposits or chalk, and rock layers, ending up in a pocket of accumulated groundwater (water trapped between rock layers beneath the earth’s surface).

While the water flows through these various layers, the water picks up minerals, such as calcium, magnesium, and iron, becoming hard water. The mineral concentration levels depend on the composition of the soil it flows through and how far the water has traveled to reach an underground water reservoir. 

The Effects of Hard Water and Why It’s Softened

Hard water can wreak havoc on plumbing systems in homes and buildings for industrial or commercial purposes.

The excessive amount of minerals in hard water attaches to the sides of drains and in filter screens, building up over time. As the minerals build up, they cause issues such as clogs and corrosion to plumbing systems. Water softening is implemented in these cases to prevent plumbing (and your wallet) from suffering.

Hard water can also damage appliances that use water, such as your refrigerator and washing machine. And it also affects your skin and hair when you take a bath or shower, leaving your skin dry and your hair brittle.

The Effects of Hard Water on Houseplants

Watering your houseplants with hard water long-term creates a harsh soil environment for houseplants. A high concentration of minerals that the plants only require in small amounts hinders the ability of the roots to absorb what they need. You may even notice build-up occurring when the water leaves behind visible white residue on the top layer of the soil.

Excess mineral concentration in the soil can deprive your plant’s roots of water. The high concentration of mineral salts in the soil will hold the water and prevent the roots from absorbing it, drying up the roots and potentially killing the plant.

At this point, you may think softened water is the better option for your houseplants and yourself. But you may want to rethink that after learning about the process of softening water.

The Water Softening Process

The most effective way to manage hard water is by softening it to remove the excess minerals. Water softening involves adding chemicals, forming insoluble precipitates, or by ion exchange to soften the mineral concentration levels. Softening water can also include adding a salt-water solution to flush and remove the minerals the system has collected. 

Using Chemicals

Chemically treating hard water typically entails using chemicals including, but not limited to, chlorine, ammonia, and lime. A combination of lime and soda ash (sodium carbonate), called lime-soda, is also used. Lime softening (lime-soda treatment) removes calcium and magnesium salts by precipitation. 

In municipal water, chlorine and chloramine (chlorine and ammonia) are typically used to treat and soften the water. These chemicals are used in two ways, chlorination and chloramination. The CDC states chlorine levels of up to 4 milligrams per liter are safe for drinking.

During this process, microorganisms and dissolved organic matter are also removed.

Ion Exchange

In the process of softening water using ion exchange, the harder minerals such as calcium and magnesium are filtered through resin beads charged with sodium or potassium ions.

While water passes through the resin beads, calcium and magnesium are extracted and replaced with sodium or potassium. When the beads max out and no longer absorb the hard minerals, it needs to be recharged. 

To recharge the beads, they are cleansed with a highly concentrated salt-water solution from salt added to the tank. This process removes the hard minerals from the beads, replacing them with sodium or potassium. Once the cleansing process is complete, the salt water solution is flushed with fresh water, and the process starts all over again.

Ion exchange is the most commonly used method in households. 

How Softened Water Affects Houseplants

Salt is an essential component of removing the minerals causing hardness in the water, so soft water typically contains a higher level of salt. As the salt builds up in the soil over time, it can be detrimental to the health of your plants. 

In addition to using the salt solution, the filtration process eliminates microorganisms and other beneficial components that may aid plant health. 

The Effects of Salt on Plants

As discussed in my other article about watering houseplants with bottled water, salt will significantly impact the health of your houseplants. 

Natural salts occur in soil, but usually in small amounts safe for plants. 

When added to the soil in excess amounts, salt throws off the natural balance and stresses your plant. Salt limits the ability of the roots to transport water to parts of the plant that need it, leading to dehydration and leaf burn.

It also interferes with nitrogen uptake, which reduces growth and hinders reproduction. 

Recognizing Build-up

The signs of salt building up in your potting soil is similar to overfertilizing your plants:

  • Chalky substance on the top of the soil
  • Yellow and wilting leaves
  • Brown leaf tips
  • Stunted growth

If this happens, you’ll need to remove excess salt from the soil and help your plant heal from the shock.

Treating Salt Contaminated Soil

If you can catch it in time, you can treat your potted plants with a good soil flush, known as leaching the soil.

First, remove the chalky residue by removing the soil surface (but no more than ¼-inch or 0.64 cm of the top layer).

Pick off all the yellowed and dying leaves and give the soil a long watering using distilled or filtered water to rinse out as much of the salt as you possibly can.

To ensure your plant isn’t sitting in soggy water, allow the excess to drain from the base of the pot completely before returning the pot to its previous spot.

When you leach the soil, you’re flushing out the good with the bad, so adding diluted fertilizer (or something like diluted aquarium water) will help replenish the nutrients needed for your plant to heal.

If you usually bottom water or feed your plants, switch to top watering after 4-5 cycles of bottom watering to force any leftover salts to drain out of the holes.

You can read my other article on how to effectively soil drench your potted plants here: How to Effectively Soil Drench Your Potted Plants

Optimal Watering Practices for Houseplants

A separate faucet outside that bypasses the softening system can limit possible salt buildup. This way, you can use your unaltered hard water by making it safe in a more organic way. There are a few ways to naturally soften water to make it safe for houseplants and your outdoor garden.

Sterilizing your softened or hard water by boiling it will improve its quality, ready for use on your plants. If you choose this method, ensure the boiled water has cooled down to room temperature before using.

Boiling water for about 15 minutes can speed up the dissipation of chlorine. However, if your municipal water uses chloramine, using a filtration system with active carbon filters will be more effective in removing the chemical.

Volcanic rock is a natural material you can also use to filter water and is widely used to help with drainage for potted plants. As the water flows through the rocks, minerals are absorbed, lessening the concentration.

Of course, rainwater is naturally soft and can be collected to use for your outdoor gardening and houseplants. That will be an easy and recommended solution if you have a way to collect rainwater. Rainwater is nitrogen-rich and contains minerals essential for plant health and development. 

Final Thoughts

Watering your houseplants with water containing salt and chemicals from the softening process will negatively affect the health and development of your plants. If you don’t catch a buildup in time, your houseplants may experience growth problems. Treat when you notice a salt build-up in the soil by leaching the soil.

Use high-quality water for your plants instead water containing salt or chemicals. If possible, collect rainwater for optimal results and balanced plant nutrition. Otherwise, try natural ways to soften your hard water without including harsh additives.

Dr. Moritz Picot

Dr. Moritz Picot is a horticulture enthusiast and the founder of TheGrowingLeaf.com, where he serves as the lead content writer. He established the website in 2022 as a valuable resource for both gardening aficionados and beginners, compiling all the gardening tips he has accumulated over the past 25 years. Alex has a passion for nurturing plants, transforming backyards into inviting spaces, and sharing his knowledge with the world.

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