There is an increasing number of environmentally conscious people in the world who make it a point to avoid wasting resources. It may no longer be surprising that some plant parents use greywater for their plants’ regular watering needs. However, is it okay to use dishwater on your plants?
You cannot water your plants with dishwater. Although dishwater can help reduce waste and be beneficial for your plants at some point, the disadvantages far outweigh the benefits. Dishwater may contain food particles that can attract pests or harmful microbes that can damage your plants.
You may have found recommendations online or from gardening magazines about using dishwater for your plants. However, it may not be as beneficial as some people claim. This article will explain why dishwater is not safe and what you can do to make it safe if you want to give it a try.
Why Is It Not Safe To Water Your Plants With Dishwater?
One popular way to reduce our negative impact on the environment is to find ways to utilize waste products. This way, we can avoid wasting resources needlessly, such as clean water. That’s why many people have resorted to using household wastewater for gardening or agriculture.
Cloudy or dirty wastewater is often referred to as greywater due to the presence of residues. Some sources of greywater at home include:
- Dishwater from the dishwasher
- Water from the kitchen sink
- Laundry water
- Water from the shower drains
- Water from the bathtub drains
- Water from bathroom sinks
In most communities in the US, every household generates significant amounts of wastewater daily, which goes into the community sewer systems. The wastewater is then transported to a treatment facility, where it is treated to remove most organic and large solid waste particles.
After which, the treated water goes back to homes for non-potable uses, such as in agriculture or home toilet flushing. This system is common and beneficial for areas with a limited supply of fresh water, especially those that require intelligent ways of recycling wastewater.
Below are some reasons why water treatment facilities are vital for communities:
- It helps prevent the contamination of natural freshwater bodies like rivers and lakes.
- It provides alternative water sources during severe drought or water shortages.
However, many communities lack this system, and residents may try to collect dishwater by themselves for garden use. Although it seems like a clever way to recycle dishwater, it is not recommended.
It is not safe to water your plants with dishwater because it may contain food particles, harmful microorganisms, or toxic chemicals from your dish soap. If you use dishwater directly to water your plants, you are skipping the essential wastewater treatment that helps remove these contaminants.
Moreover, even if there is a water treatment system, the technology may be insufficient in reducing or eliminating harmful contaminants or pollutants.
Let’s look further into how these factors make it unsafe to water your plants with dishwater:
Dishwater May Contain Food Particles
Leftover food particles attached to your cookware and utensils will drain along with greywater after using your dishwasher. These particles may attract insects and rodents to your garden and cause severe damage to your plants.
In addition, decaying food particles or organic matter may also promote the growth of fungi or mold, which, although not directly harmful to your plants, may be dangerous when inhaled by people with hypersensitivity.
This is especially true if you use dishwater for indoor plants. The fungi will eventually create spores and contaminate your indoor air, effectively reducing its quality. It might then compromise the health of the people living in the house.
Greywater From the Dishwasher May Contain Harmful Microbes
Untreated dishwater may contain harmful microorganisms, such as bacteria and fungi. These pathogens typically come from improper food handling and poor hygiene.
Using dishwater contaminated by pathogens to water edible plants like leafy vegetables and fruits may pose serious health risks to the people who consume them. Even house pets that snack on dishwater-contaminated houseplants may be affected and fall ill.
Some common pathogens found in dishwater include:
- Escherichia coli
- Pseudomonas aeruginosa
- Stenotrophomonas maltophilia
- Acinetobacter baumannii
- Candida
- Cryptococcus
Once these microbes get washed along with dishwater and are introduced to the garden, they may thrive and cause infections in immunocompromised humans and animals.
Dish Soap Residues May Contain Chemicals Bad for the Soil
Many gardeners use diluted dish soap to kill and ward off insects and pests from their plants. It proves that dish soap can be safe for plants as long as it is diluted in water.
In view of this, one would think that since wastewater from the dishwasher contains highly diluted dish soap, it must be safe for plants.
Sadly, that’s not always the case. Many dish soaps or detergents used in dishwashers typically contain excessive salt that can be bad for the soil. Temporary and short-term use of dishwater for plant watering needs may not cause serious problems.
However, long-term application of salt-rich dishwater may result in more compact soil, making it impenetrable with water. In addition, the plants may absorb excessive sodium and chloride, which can cause a deficiency in other essential nutrients, such as:
- Nitrogen
- Phosphorus, and
- Potassium
Moreover, if your dishwasher or home water filtration system uses water softeners, it can introduce more sodium into your dishwater. The high levels of sodium from your water and dish soap can be detrimental to your plants, especially if used for long.
Setting Up a Greywater Irrigation System Can Be Costly
Another downside to using dishwater for your plants is that it can be costly to redirect a built home’s drainage pipes from sewer lines to your garden’s irrigation system. That’s why it’s best to consider greywater recycling before constructing your home.
Nonetheless, even if you already have a built home but still want to set up an irrigation system using the water from your dishwasher or kitchen sink, it is possible. However, it will take some time to set up and can prove costly because you’ll need your own greywater filtration system.
Another concern here is the maintenance and efficiency of your greywater irrigation system. The system typically removes most organic materials and contaminants from the water but may not be able to remove every harmful substance.
Depending on the wastewater regulations in your community, you may also need to regularly test the quality of your greywater to ensure that it won’t pose any threats to the environment.
How To Make Dishwater Safe for Your Plants
Some states may have regulations regarding proper wastewater disposal or management and may not permit households to use greywater for irrigation. So if you’re planning to start a greywater irrigation system for your home garden, you must check with your local authorities first.
If your community allows it, you can start carrying out strategies to make dishwater safe for your plants. Here are some of them:
Use Dish Soap or Detergent That Is Safe for Plants and Soil
Liquid dish soaps or detergents are generally safer for plants than powder ones because they are more readily soluble. Moreover, it’s crucial to use a cleaning product that contains little to no salt (sodium chloride).
Dish soaps that contain bleach can also be toxic to plants, so avoid such an ingredient.
Despite their sodium content, dish soaps containing sodium lauryl sulfates (SLS) are safe to use because the chemical is water-soluble and biodegradable. This means that the chemical will be degraded into non-toxic forms by the time it reaches your garden.
Don’t Let Dishwater Touch the Plants’ Edible Parts
When using greywater, including dishwater, for your plants, it is best to install an underground irrigation system. It will prevent the water and the potentially harmful contaminants from touching the edible parts of your plants, such as
- the leaves
- fruits, and
- flowers
The underground irrigation system also keeps the water close to the roots for absorption, reducing the risk of contact between humans and pathogens during gardening activities.
Final Thoughts
Dishwater is not ideal for plants because it typically contains contaminants that can harm your plants and garden soil.
Fortunately, there are ways to make dishwater safe for agricultural irrigation, such as using a water treatment system. However, it can be costly and challenging to install and maintain. Moreover, your local government may prohibit it.
Although it’s not recommended, you can try to use dishwater on your plants. Just weigh the pros and cons to help you decide whether it’s worth trying.
I’ve written another article on watering vegetables with greywater. Don’t miss it: Can You Water Vegetables With Greywater?
