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How To Dispose of Hydroponic Wastewater the Right Way

How To Dispose of Hydroponic Wastewater the Right Way

When gardening hydroponically, plants are grown using water and nutrient solutions instead of traditional soil. This approach presents a viable and efficient solution for cultivating plants in small areas.

Periodically, wastewater from the hydroponic system will need to be removed and disposed of.

What is hydroponic wastewater? Hydroponic wastewater is the water removed from a hydroponic system. It contains high concentrations of the added nutrient solutions that are necessary for plant growth. Incorrectly disposing of hydroponic wastewater can introduce excess nutrients into the environment and disrupt local ecosystems.

Many areas have laws about proper wastewater disposal to protect the environment, so knowing how to handle the disposal of your hydroponic wastewater is critical. Let’s jump right in.

Hydroponic Wastewater Disposal Options

If you have a hydroponic system, there are a couple of options for you to safely dispose of your wastewater. Choose the method that works best for your situation.

Use To Water Potted Plants

To use the nutrient-rich wastewater in your garden, you must first dilute it with an equal amount of tap water. This mixture can be used to water self-contained potted plants.

You should not use this mixture in your garden because the nutrient levels are still high and can contribute to fertilizer runoff. 

Pour It Down the Drain

The pipes in your house are capable of handling the high levels of nutrients in the wastewater.

Water treatment facilities clean the water, removing the nutrients before it goes back into circulation.

Purify Wastewater

If you are running a large hydroponic operation, it may be worth investing in a system to purify your wastewater. A small filtration system can cost around $200.

The most common systems use filtration and reverse osmosis to remove particles from the water. It is important to test your water after you purify it.

Ideally, the water will have a pH around 7.0 and EC (electrical conductivity) near 0.0.

This is how you know that your system has successfully removed the nutrients and you can now safely dispose of the water in any manner.

Why You Shouldn’t Dump Hydroponic Wastewater Outside

High concentrations of nutrients disrupt the natural balance in an ecosystem. Specifically, nitrogen and phosphorus can lead to algae and phytoplankton blooms.

These blooms choke out the oxygen in waterways, killing plants and animals.

Even if you do not live near a water source, nutrients from hydroponic wastewater can still cause problems due to runoff.

General Guidelines for Dealing With Hydroponic Wastewater

First off, check local laws about the proper disposal of hydroponic wastewater.

Since runoff can travel away from your operation, it is important to check the laws of surrounding areas that could also be affected.

If you are using your wastewater to water potted plants, you should dilute the nutrient-rich wastewater until the pH is between 5.5 and 6.5 and the EC is 1.2-2.0.

To dispose of wastewater outside, it will need to be purified and have a pH of around 7.0 and EC close to 0.0.

How Often Should I Flush My Hydroponic System?

You’ll need to top off your hydroponic system as necessary and fully flush the system approximately every 2-3 weeks.

The exact time frame will depend on the size of your setup, how “thirsty” your plants are, and how frequently you are adding additional water. 

Can You Use Hydroponic Wastewater in Your Garden?

A person wearing green gloves using a yellow watering can to water four potted flowers.

Hydroponic wastewater can be diluted and used to water a container garden. It is important that you only use wastewater for potted plants that will not drain outdoors.

When it rains, the excess water can still carry the nutrients into the environment.

Do Plant Nutrients Expire?

Plant nutrients can expire. Check the package for the expiration date.

What To Do With Expired Hydroponic Nutrients

Expired nutrients can be disposed of in your garbage. However, if your product has added pesticides or herbicides, it is considered household waste.

The package may also be labeled as hazardous. Contact your local waste management company to find out proper disposal directions.

Related Questions:

Can Hydroponic Water Be Recycled?

Hydroponic water can be recycled once it is purified. Since the water runs through the system multiple times before it is flushed, it can pick up bacteria, mold, and other pathogens.

To protect the health of your hydroponic garden, you will need to purify the water to recycle it.

How Do You Dispose of pH Down?

To dispose of pH down buffers, you’ll need to first neutralize the product. Use an alkaline substance (like baking soda) to bring the pH up to at least 6.0.

You can now pour the product down the drain with lots of water. Ideally, you will pour 100 times more water than the product used to ensure that it does not damage the pipes. 

An easier method for disposing of pH down is to contact your local waste management company to see if they have a facility that accepts household waste. 


Wastewater is a necessary component of any hydroponic operation.

Even though hydroponic solutions use less water and resources than traditional gardening, incorrectly disposing of wastewater can cause damage to the local environment.

Dispose of your hydroponic wastewater appropriately to maintain the health of your garden and plants.