How To Find Out If Your Tap Water Is Safe For Houseplants

Most people water their houseplants with tap water without even thinking about it. Generally, most plants will do just fine with tap water, though some more sensitive plants might not appreciate it. To water your plants appropriately, it is good to know what there is in your tap water and if it is totally safe for plants in the long run.

Potable tap water is generally safe for plants as fluoride and chlorine levels are regulated by the local authorities to suit human consumption. For plants, chlorine levels in tap water should not exceed 50 ppm. Fluoride however should not exceed 1 ppm; higher amounts need be filtered out.

You can easily find out what levels of chlorine, fluoride, and other ingredients your tap water has and adjust your use of it for your houseplants accordingly. In this post you will find all you need to know about tap water and houseplants.

Is Tap Water Safe For Houseplants?

As a general rule, tap water is safe for houseplants, though higher amounts of chlorine and especially fluoride can damage plants in the long run.

If you drink your tap water yourself without filtering it and it doesn’t have a strong chlorine smell to it, then using regular tap water for your indoor plants is most probably fine.

The only thing you might want to check is the softness/hardness of your tap water: Very soft water contains more sodium ions which means it is much saltier. In the long run, too much salt will be deposited in your plant’s soil which can harm your plants.

Obviously, if you want to treat your plants with only the best or you have some very sensitive plant species, there are plenty of ways to upgrade your tap water or use other types of water which I will discuss a little later in this post, so stay tuned!

Tip: The health of your plants does not just depend on what water you use, but relies a lot on how you water your plants. I share plenty of practical tips and knowledge on how to water your plants in the post linked right here.

What Is It About Tap Water Than Can Harm Plants?

It is mainly the following issues that need be considered when using tap water for plants:

  • Water hardness level
  • The pH level of water
  • Level of chlorine
  • Level of fluoride

Note: Except for the pH level, the water hardness as well as levels of the other ingredients are usually noted in the unit ppm. This means milligrams per liter and is reported in the unit parts-per-million (ppm).

Water Hardness Level: Especially Soft Water Can Harm Your Plants

Water hardness levels of 30 – 60 ppm are considered ideal for plants.

Water harder than that will contain too many calcium and magnesium ions (too many limescale deposits), and water softer than that will contain too many sodium ions (too much salt).

If you are cleaning off limescale deposits in your kitchen and bathroom regularly, then your water is probably too hard. Though generally, water that is too soft is more harmful to plants than water that is a little too hard. Soft water contains much more salt which can damage a plant’s root system rather fast.

The pH Level: Plants Prefer Slightly Acidic Water

Another factor to consider is the pH level of water. This tells you whether water is acidic (“sour”) or alkaline (“sweet”). On the pH scale, a level of 7.0 is considered neutral or balanced between acidic and alkaline.

Plants do not have a sweet tooth: As a general rule, plants prefer slightly acidic soil. To achieve this, plant water used needs to be slightly acidic as well.

A pH level between 5.0 and 7.0 is considered ideal for plant water.

Tap water generally has a pH level of anywhere between 6.5 and 8.5. Hence, it is worth checking the exact pH level of the tap water in your living area to know whether it is acidic enough for your houseplants.

Chlorine: Potentially Harmful In High Amounts

Chlorine is not per se harmful to plants. If only low quantities are present in plant water, plants will barely take it in. High amounts though can damage foliage growth.

As to the tolerable levels of chlorine in plant water, there are different opinions among experts. Some state that an upper limit of 5 ppm of chlorine per liter is recommendable for plant water. Other sources speak of limits as high as 100 ppm of chlorine for plant water.

Hence, I recommend using water with 50 ppm of chlorine at the max.

Getting rid of chlorine in tap water is luckily relatively easy – I’ll give you some practical tips on that a little further down in this post.

Fluoride: Best Avoided Completely

Fluoride can be very harmful to plants. It inhibits photosynthesis as well as other metabolic processes by moving up from the roots and accumulating in the leaves of the plant. This is probably the one ingredient in tap water that causes experts to strongly veto against using tap water for plants.

Plant water should contain no more than 1 ppm of fluoride per liter while less is always better.

Since the 1960ies, many governments around the world turned to artificially adding fluoride to tap water to address growing caries issues among the population. However, this trend has decreased tremendously in the last decades with many nations no longer adding any extra fluoride to their tap water.

Hence, even though experts generally warn against using tap water for plants due to its fluoride levels, depending on where you live, the fluoride levels might already be very low again.

How To Find Out If Your Tap Water Is Safe For Plants

First of all, do you drink your tap water without thinking twice because it tastes good and its what everyone does where you live? Then chances are already very high that your tap water is safe for plants, too.

That said, you might still want to find out exactly how much of these potentially harmful ingredients such as chlorine or fluoride are in your water.

To find out, you can either check the local authorities or the local water purification plant’s website for their data on what ingredients the drinking water of your area contains. They should provide a list of all ingredients your water contains naturally as well as of those that are added artificially during the purification process.

Another, though costlier, option is to get your tap water tested in a lab. Any laboratory can test your tap water but there are also specific water analysis labs that will do this for you.

Tip: I know that in some European countries, you can even get tap water tested at pharmacies which costs much less than sending a sample to a lab and you will get the results quite fast. It might not be as detailed an analysis but it does the trick for what you need to know about your tap water. You can check whether pharmacies offer this service where you live.

What Else Is In Tap Water?

Depending on where you live, tap water not only contains harmful ingredients but also many nutrients that are beneficial to plants, such as magnesium, nitrate, and potassium.

What ingredients are in tap water can vary according to the living area and national regulations. Though the ingredients won’t be drastically different as all potable tap water is made to be safe for humans to drink.

Just to give you an idea of all that tap water contains, here’s the list of what the tap water where I live contains. Please note that I live in a European country and water purification regulations in other parts of the world might differ.

  • Hydrocarbonate
  • Calcium
  • Sulfate
  • Chlorine
  • Natrium (or sodium)
  • Magnesium
  • Nitrate
  • Silica (or silicon dioxide)
  • Potassium
  • Fluoride
  • Aluminum (negligible level)

In the case of my tap water, according to the local water purification plant’s data, it contains only 16.7 ppm of chlorine and 0.15 ppm of fluoride which makes it pretty safe to use for plants.

Now, go ahead and check out what your own tap water contains!

Tips To Make Your Tap Water Better For Plants

Let It Sit For 1-5 Days

The easiest way to better the quality of your tap water for plants is to pour it into a container and let it sit for 1-5 days. This will help the chlorine to dissipate. The process will be faster or slower depending on how much surface area the water has in the container: The more surface area, the faster the dissipation of the chlorine.

With this method, high amounts of chlorine can be dealt with. Also, heavy metals that might be present in tap water, too, will sink to the bottom of the container. Try not to stirr up the water before watering and do not use the bottom part of the water. That way you can avoid some of the heavy metals in the water.

What cannot be dealt with using this method are the levels of fluoride or other ingredients as they do not dissipate or sink. For that, you need to filter your tap water.

Filter Your Tap Water

The easiest way to filter your tap water is by using a regular household filter pitcher. There are plenty of brands that sell such filter pitchers (such as BRITA or ZeroWater). It doesn’t cost much and the filter usually only needs to be replaced every couple of months.

A slightly more costly option is to install a faucet attachment in your kitchen which filters the water. This makes for a more sustainable alternative as the faucet is a permanent installment in your kitchen.

Tip: Filtering tap water is not only beneficial to your plants but also to yourself as you can drink better quality water from now on!

Add Natural Fertilizers To Your Plant Water

Your tap water might already be of good quality and there is no need to filter it but you still want to give your plants that little extra care? There are plenty of natural beneficial ingredients you can use as fertilizers in your plant water.

You’ll find lots of information on so many different ingredients to use, it is hard to keep an overview. Which is why I have summed up the most beneficial natural ingredients and what their effects are on plants in the post linked here.

What Water Is Best For Houseplants?

Water is not “just” water. Even though it seems to be a transparent, tasteless liquid, it comes with a wide variety of dissolved nutrients which can have different effects.

Rainwater proves to be the best plant water, while recommendable alternatives are fish tank freshwater, filtered tap water, or distilled water in combination with fertilizer.

I explain all about the pros and cons of different water types as well as how to prepare the best water for your plants in this post right here.

Do Plants Need Drainage?

Drainage holes are essential to most plant types as they improve airflow, wash out excess water, salt as well as harmful substances and thereby decrease chances of root rot and soil diseases. A well-drained soil provides regular oxygen flow for roots to absorb water and nutrients effectively.

Learn all about how to create appropriate drainage for your indoor plants in my post linked here.

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