Is Dehumidifier Water Good For Plants? 💧

Is Dehumidifier Water Good For Plants

Reading Time: 8 minutes 🍃

Those who make use of a dehumidifier to remove the water from the air inside their houses can be forgiven for wondering whether there are any alternative uses for the water they collect. One option that the gardeners among them might wonder about is whether they can use the water from the dehumidifier to water their plants.  

Dehumidifier water can be used to water plants. It is close to distilled water in its composition, so it can be used in the garden without any issues. However, if there are contaminants in the humidifier, this can cause issues, so care should be taken. 

It seems like dehumidifier water should cause no problems at all in the garden, but there are a few issues to be aware of. Read on to learn more about what steps you might want to consider when looking to make use of the water from your appliance in the garden.

Why Is Dehumidifier Water Good for Plants?

Dehumidifiers are an increasingly popular appliance in the home and have seen significant increases in sales over the last decade. A dehumidifier will remove water from the air, which is often referring as humidity. It does this by utilizing the process of condensation — a process by which water in its gas state is converted into its liquid state through the process of cooling.

This process, where water can have its state transformed, is a reflection of the amount of energy held by the water molecules. When water molecules are close together, they have a relatively low level of attraction toward one another. As they gain more energy, they are able to break free of that attraction and move more freely. This is what helps determine the state of water, of which there are three:

  • Solid (ice)
  • Liquid
  • Gas (water vapor)

This is why when the temperature of the water is very low, and it is in its ice form — where the water molecules have no energy to escape the attraction of the molecules around them and so are packed densely together, forming hard ice. As the temperature increases, more and more water molecules are able to escape their local attractors and travel more freely. This continuum of the temperature of freedom of movement for the water molecules is what the state changes from ice to water to vapor represents.

A dehumidifier, then, takes the water in the air and cools it in order to reduce the level of molecule movement. It does this by sucking in air from the room in which it is located and then passing that air over metal coils that contain refrigerant. This refrigerant, coupled with a small compressor, is what keeps the metal coils very cool, and as the air passes over the coils, the water molecules in the air are cooled — with some of those molecules reaching the temperature required for a state change to water.

This water is then collected in a container so that it can be disposed of. 

See more info on using dehumidifier water here. 

The fact that this process has occurred in order to collect the water is critical to why the water is safe — while there may be many compounds in the air or in liquid water from another source, by going through the process of condensation, we know that the water is pure. This means that the water collected in a dehumidifier is likely to be very close to the qualities of distilled water.

As a result, applying water that has been collected in the container of a dehumidifier is absolutely fine for plants; water is, of course, a vital component in the growth of all living things, and so applying this pure water to plants will help them thrive.

However, there are a couple of issues to be mindful of:

  • Bacteria and Mold
  • Contaminants from the container

Bacteria and Mold

While the water collected is fine at the point at which it has turned to its liquid form, the reality is that this takes time, and so the water in the container of the dehumidifier is likely to be sat around for a while. This increases the chance of bacteria and mold growing within the water. 

The rate at which the dehumidifier will be able to fill the container will depend on a number of factors, such as the size of the container, the power of the humidifier, and the amount of humidity in the room; however, they typically take at least a few hours to fill. In addition, many users may leave their appliance in situ for a longer period of time, turning the appliance on intermittently but not actually emptying the container if it is not full. This is the perfect environment for the growth of bacteria and mold.

Even if the water contains bacteria and mold, it is unlikely to make a significant difference to the health of the plant. However, gardeners applying the water to their plants should be especially mindful of edible plants which are not processed before cleaning.

For example, applying water to a cabbage poses limited risk as the cabbage can be expected to be cooked prior to eating, ridding the plant of any lingering microorganisms. Applying the water to lettuce, though, could pose significant risks to humans when eaten if special care has not been taken to wash the produce very thoroughly. It’s for this reason that the general advice is not to apply water from a dehumidifier to edible plants. 

Contaminants From the Container

Another possible risk factor is that the container used to collect water in the dehumidifier has already been exposed to contaminants.  

The most common examples of this are soap and disinfectant solutions that have been used to clean the container without having been fully rinsed off the material. In this case, it is unlikely that the cleaning chemicals will be in high enough concentrations to have any impact on the plants.

If the container has been exposed to very high levels of soap solutions, though, it should not be used on plants because of the damage it can have on the composition of the soil. The composition of the soil is extremely important because it plays a critical role in the ability of plants to grow normally. 

Soil Structure and Composition

The role of soil structure and composition cannot be understated; it is the core factor that influences the ability of a plant to grow effectively. It plays a number of roles, from the anchoring of roots to ensure that plants can remain situated effectively to the storing of nutrients for the plant to absorb over time.

Soil is a complex system. It has many different contributors that come together over time to create an environment in which plants can grow. If soil undergoes too much interference, either natural or by humans, it can cause lasting problems for the soil. Examples of this are:

  • Soils that end up very sandy (which are highly subject to erosion)
  • Clay-heavy (which struggles to drain water effectively)

Another factor that plays a role in soil quality is the volume and type of microorganisms in the soil. These creatures are extremely important, facilitating the breakdown of organic matter in the soil for it to both create and more readily give up nutrients that the plant needs. It also, in turn, plays a role in the structure of the soil as the composition is directly dependent upon the extent to which much of this activity is possible.

This is the problem with applying soap to the soil. Soap will break down the cell walls of many microorganisms and therefore reduce their numbers, which can reduce the level of decomposition of organic matter that can occur. It’s also an issue because it can contribute to imbalances of microorganisms in the soil.

When Is the Best Time To Use Dehumidifier Water In The Garden?

Generally speaking, dehumidifier water is not especially better or worse than tap water. This means that often, because of the volumes of water usually required to water a garden, it’ll be easier to use the garden hose rather than the dehumidifier water.

There is one special case, though, where the use of dehumidifier water comes into its own. When the local areas are experiencing very high heat, hosepipe bans can sometimes be put into place. These ensure that the local water reserves are saved, with water use in the house prioritized — making all water available to a household extra value from a usage perspective.

During this period, the specific rules can vary depending on where you are, so they should be checked to ensure that they are being followed. Generally speaking, though, while the use of the garden hose is banned, water from the home is allowed — even for the garden.

This might seem counter-intuitive as there’s no real difference between the water from the garden tap and indoors. However, it’s a question of the volume of water used by the different styles of usage. Outdoor water usage tends to be left on for a long time, meaning a greater volume of water is used — and its often the case when using devices like sprinklers that more water ends up being used than is needed when the devices are left for long periods of time without complete oversight.

This is the perfect opportunity to reuse dehumidifier water in the garden. It can fulfill a brilliant purpose — helping provide the plants with water during a time when the garden hose is not allowed to be used. This is especially important because the hosepipe bans tend to come into effect during the hottest weather — the time when plants need water most.

Can Dehumidifier Water Be Used on House Plants?

As we have seen, dehumidifier water is theoretically closest to distilled water. This type of water is much like rain in its purest form, so it’s no surprise that house plants will also appreciate the application of the water.

The main consideration, though, is how long the water has been sitting in the dehumidifier container. With the onset of bacterial growth and mold in water that has been left for a long time, it is especially important that this is not the case if you intend to use the water on houseplants. 

This is because if the mold and bacteria are in the indoor environment where the air is being breathed in, it means that there is an increasing likelihood of the members of the household breathing in bacteria and spores that can be released into the air. 

If the water is frequently emptied and the container cleaned periodically (and rinsed thoroughly), then there should be no issue with using the dehumidifier water on indoor plants too.

In fact, using dehumidifier water on house plants is a particularly good use case because it allows conscientious homeowners to reduce their water footprint by reusing the grey water that the dehumidifier provides. 

Reducing water consumption is important because it has lots of broader impact. Using less water requires less energy, which is a perfect example of having a direct reduction in the amount of fossil fuel usage required in order to supply water. 

Much of the water that makes its way slowly but surely into houses originally starts in natural areas of high-water volumes, such as lakes and wetlands. These environments are put under pressure by water consumption, and so any opportunity to reduce the usage can benefit areas such as wetlands. This, in turn, will have a positive effect on the native populations of those areas, which can frequently include wildlife such as fish, herons, water voles, and otters.


It’s clear that dehumidifier water is generally no problem at all when considering use in the garden. However, as there are a few minor risks of contamination attached to it, you should be careful about the way in which you go about it. As long as you are aware of the issues, though, there are some clear circumstances where using the grey water that comes from your dehumidifier is a fantastic way to reduce your overall water consumption.


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