Hard or Soft Water for Houseplants – What to do?

The quality of your tap water is an ongoing issue for houseplant owners. The problems you face will differ depending on your area and the type of treatment the water receives before it comes out of the faucet. However, particular questions do arise when it comes to using it for your indoor plants.

  • is your tap water safe to use for your plants?
  • how do you treat different types of hard or soft water?
  • what type of water is the best for plants?
How to Fix Hard Water for Plants

We’ll be answering these questions and more in the article below, plus addressing some of the commonly asked questions.

Hard Water – What is the Problem?

Water is generally referred to as ‘hard’ when it contains high concentrations of chalky or metallic minerals. The type of minerals can vary between different areas, but some examples of trace elements are calcium and magnesium.

There are some visible side effects of using hard water in your daily routine. Such as stains on your crockery after it has been washed, skin feeling dry after rinsing your hands or face with tap water, or in our case white marks left on the foliage of your houseplants (check out how to get rid of hard water marks on leaves HERE).

The problem with using hard water on your plants is it can have detrimental long-term effects on their health. Plants do not absorb the minerals in these quantities, and they can accumulate in the soil.

What about soft water?

Unfortunately, the same applies to soft water. The difference is soft water contains higher concentrations of salt (rather than calcium and magnesium).

Using soft water is arguably worse than hard water. Because not only will the salts build up in the soil, leading to long-term issues with your plants’ health. Higher sodium content (provided by the salts) will affect your plant’s water absorption rates.

What water is best for houseplants?

Where possible, we recommend using other natural or filtered choices for water, like rainwater, and RO (reverse osmosis) water. Even bottled drinking water is better than using soft or hard tap water for your plants – however, this is generally not an economical solution.

hard water for houseplants

How to Treat Tap Water for Your Plants

The good news is there are some treatments you can perform on your tap water to make it safe to use for your plants. The treatments neutralize the excess minerals and compounds.

Let’s take a look.

How to Treat Hard Water

To eliminate or counter the presence of harder minerals in tap water, there are several different approaches.

  • Reverse Osmosis (RO) Systems – using a RO system is the cleanest way of ensuring all unnecessary minerals are removed from your tap water. In short, an RO system pressurizes tap water and pushes it through a process of filters that removes and collects any impurities. The result is pure H2O that usually collects in a tank because the process to filter the water is a long process.
  • Additives – another way to neutralize the minerals in your tap water is to add a solution that harmonizes the imbalance. Each additive will be specific to your local area, as hard tap water contains different minerals in different parts of the world. You should be able to find a local additive for your specific tap water at your local nursery.
  • Organic Methods – the last option is to try using organic methods for balancing the excess minerals in your hard water. There are materials that offer natural ways to filter minerals out of tap water, such as volcanic rock and carbon. By mixing these materials into your soil, they can naturally absorb the excess materials, leaving clean H2O for your plant to use.

How to Test Hardness of Tap Water

The quickest and easiest way to test the hard properties of your water is to use a home water test kit. They are readily available, budget-friendly, and simple to use, like this one from Amazon.

Here’s a quick video on testing tap water by Gary the Water Guy.

How to Fix Hard Water for Plants – Common Questions

Do I need to add extra minerals to my soil for soft water?

The salt content in soft water may be too high for some plants. Therefore it is necessary to dilute or neutralize the excess minerals in soft water. You can achieve this by adding rainwater to bring the concentration down. Alternatively, you can try natural methods by using organic materials (similar to hard water). Volcanic rock is a great option for filtering tap water. The porous properties allow water to flow through, while the minerals are filtered out.

Is hard water bad for plants?

Yes – hard water will harm your plants in the long term. The excess minerals will build up in the soil and can prevent the natural processes in your plants from functioning properly.

We recommend changing the water source you use for your plants, or using solutions that will neutralize the unused minerals in the soil.

What type of water is best for indoor plants?

Clean natural water is always the best option for plants. Collecting rainwater is a safe choice. Alternatively, distilled or filtered water will also serve the same purposes. Basically, the main thing is to introduce minimal additional minerals and chemicals to your plants in your water.