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How to Flush Hydroponic Plants

How to Flush Hydroponic Plants?

    Before you get to know the timings and process to flush hydroponic plants, it’s essential to understand the meaning of flushing at first. In general terms, flushing is applying only the water (with a special flushing agent) to the root zones of hydroponic plants.

    The task of flushing comes before the task of harvesting. It is done to ensure that nutrition is available to all the hydroponic plants at all times. Flushing your system water pots with just water allows them to retain the remaining nutrients.

    The experienced hydroponic growers can well understand the importance of this flushing. While ascertaining the flushing techniques of expert growers, this article will be an ultimate guide on how to flush hydroponic plants.

    So, let’s start by answering the question, as stated above.

    How to flush hydroponic plants – Step-by-Step Guide

    There are two kinds of flushing. The first one is to flush the growing medium, whereas the second one is to flush the hydroponic plant itself. Well, both of them are important to flush to remove that ‘salt toxicity.’

    Flushing the growing medium

    Flushing the growing medium refers to flushing the excess nutrient build-up with water (a special flushing agent). It is done to remove the so-called salt toxicity from the medium. You are only required to pour that specialized agent through the medium so that the excess will drain off quickly.

    Flushing the hydroponic plants

    It is our main concern to flush the hydroponic plants. The process is almost similar except that you pour so much water with that special flushing agent over the plant.

    What you are doing here is flushing the overall body of the plant so that excess build-up of salt toxicity and other nutrients will be quickly drained.

    You can even sometimes see the physical signs of this build-up over the plant, which can be dangerous to health, especially in terms of fruits and herbs. So, the ornamental plants may not need so much flushing as eating hydroponic plants will need.

    Step 1: The first step is to drain your nutrient reservoir. You should use the most appropriate or suited technique for your particular hydroponic system. Pour this old liquid on trees, outdoor gardens, or bushes and give them a ready boost.

    Step 2: After draining the nutrient reservoir, the second step is to clean it. Remove the algae or any sediments of the present using the plastic scraper tool. Remove it properly off the sides as well. At last, rinse off the tank with enough water.

    Checkout our detailed post on how to clean the whole hydroponic system.

    Step 3: Fill this reservoir with plain water while also adding that special flushing agent. Now, you need to pump the whole thing through the hydroponic system. Also, remember to follow the usage instructions as provided on the flushing agent.

    Step 4: Discard this flushed water and fill it again with the plain water and that special flushing agent. Now, it’s time to check the pH of the water. Check it and adjust by using the pH adjusting kit if necessary.

    You need to take it to about 6.0 and operate the hydroponic system with this mixture for the next 24 hours.

    Step 5: It is the last step to flush this water and refill it with the fresh nutrient solution. Operate the hydroponic system again with this nutrient solution and let it normally run until there’s a need to change the nutrient solution.

    You can run the system with this nutrient solution for around 1-2 weeks.

    Make sure that you buy a dedicated flushing mixture to get all of this done professionally and effectively. It is why the diluted solution is always advisable.

    Well, some of the growers also use organic fertilizers to flush the excess nutrients. But, most of the experienced hydroponic cultivators do not resort to this method and thus only stick to the method of adding a diluted solution with water and flushing agent.

    All-in-all, you have three basic steps of flushing if we combine the steps given above into the main categories.

    1. Reservoir Draining
    2. Reservoir Cleaning
    3. Filling The Tank

    What is the importance of It?

    As mentioned earlier, watering your plants (with a special flushing agent) before harvesting is the process of flushing. So, why is it significant? At first, flushing is so vital if you don’t want the quality difference in your yield.

    Most of the hydroponic growers have experienced a severe issue in the quality of yield when they have practiced flushing. The next reason to flush the hydroponic plants is to eliminate excess salts and nutrients deposited over them during the harvest.

    These excess nutrients or salts need a way to get flushed out properly. Also, you don’t want their bitter and harsh taste in the final product. Therefore, flushing hydroponic plants are essential to improve the overall yield of the final product.

    As against the comments of anti-flushers, it is indeed a beneficial practice. It would be best to focus on using the specialized flushing agent to get the best out of it.

    Without further ado, let’s now come to the main topic of how to flush hydroponic plants.


    Let’s consider some expert tips to flush the hydroponics.

    • It is advised to flush the hydroponic plants in the final week before harvest. It is useful if you provide your system with PH balanced in advance before harvest. In this way, the resultant crop will not taste bitter and harsh as it used to be.
    • Don’t hesitate to flush the hydroponic system several times if it is clogged with many minerals, dirt, and other debris.
    • It’s also not a bad idea if you flush the hydroponic system after changing the nutrient solution. It is an excellent practice to keep both your hydroponic plants and the overall system in ideal shape.
    • There’s a way by which you can quickly check the removal of salt build-up from the hydroponic plants. See, you need to be a little smart here! First of all, follow all the instructions for scraping the reservoir.

    Before you flush it out with the water, check it’s TDS with the EC/ppm meter. If it is fresh RO water, the TDS must show zero.

    Then, you can check the TDS level of drained water, which must show around 500-600 because of excess nutrient and salt build-up.

    How often should You Do It?

    Timing is the key when it comes to flushing your hydroponic system. To reap the maximum benefits out of the process, you need to ascertain the right timing. Look at the following guidelines for now, as you will also be provided with information on the required material.

    • The flushing is needed between one to two weeks before the harvest of you are growing in soil.
    • It is needed almost one week before the harvest if you are growing plants in coco.
    • And, hydro plants required flushing for one to two days before the harvest.

    All you need to avoid is the common mistake of the correct determination of the harvest period. Please don’t make the mistake of determining it too early, even when it is not! It is because flushing a hydroponic plant too early before harvest may lead to improper growth.

    Disadvantages of flushing hydro plants too early

    • The growth of hydroponic plants will be stunned at the flowering stage itself.
    • It leads to lower potency because of the inability of plants to retain lower nutrients.
    • The overall appearance of the resultant hydro plant will be affected, including the taste.

    Things you need

    Given below are the main tools or things that you should have to flush hydroponics.

    • RO water or Clean water
    • Specialized flushing agent
    • Hydroponic PH adjusting kit
    • A plastic scraper to remove algae
    • pH testing kit

    Addressing the arguments of anti-flushers

    In this section, you will come across an argument by the anti-flusher along with the respective clarity over it.

    • Flushing the hydroponics is equivalent to robbing the plants of nutrients at the crucial stage of the growth cycle, which is further counterproductive and not ideal for their optimal growth.

    Clarity: Flushing never means robbing the plants of nutrients. Instead, it is a way to provide a chance to hydroponic plants to use the excess nutrients that have been accumulated in the growing cycle.

    Feeding your crops with nutrients up to the time of harvest may lead to overabundance. This overload is the cause of bad quality and thus needs to be adjusted via flushing.

    It is also important to note that substantial new growth is not at all the main goal behind this flushing task. It is because the excess flushing can also lead the crops to swell.

    • Once you feed the hydroponics with nutrients, they will permanently remain there. There is no way that you can expel or take away these nutrients from plants.

    Clarity: You can ask any seasoned cultivator regarding the nutrient burn. They know better than flushing is the only way for hydroponics to use up those excess nutrients, if any. The same logic applies to pre-harvest flushing as well.

    It is simply a productive time that you are required to give to your hydroponics to use up surplus salts, nutrients, and other compounds.

    • If flushing is the only way to make the plants’ taste better and overall effect, then the hydro plants would be tastier than the plants grown in soil because soil cannot be flushed effectively.

    Clarity: The argument that the plants grown in soil cannot be flushed effectively is wholly wrong. In fact, you flush the plants grown in the traditional soil even if they take a longer period to get flushed.

    • The withholding of nutrients leads to stress situations in hydroponics plants, which are further an anti-growth phenomenon rather than an encouragement.

    Clarity: However, the argument is true that withholding nutrients can lead to stressful situations in the plants. But, some plants need these defense compounds. Most of the plants desire only these constituents for optimal growth.

    • Pseudoscience’ is what is called ‘Flushing,’ which is not backed or supported by any legitimate scientific research.

    Clarity: It is a completely absurd notion that flushing is pseudoscience. There are many microbiologists, Ph.D. botanists, and hormone specialists in organic chemistry who are working solely to study the cultivation and best practices for hydroponic plants.

    And, they completely deny this argument!

    Flushing Agent

    Arriving at the best choice of flushing agent from a range of options may be pretty hard if you don’t know your budget and hydroponic system. It is because narrowing down the selection is based on these two factors.

    The cases can be different from different growers based on the system. Some growers also use simple dish soap or hand soap to flush between the crops. And, they feel that one drop per gallon is more than enough.

    Other effective options include hydrogen peroxide or bleach. It is further dependent upon the growing media in your hydroponic system to use a specific flushing agent.

    For instance, if you are using stone wool or coco, then the flushing agent with enzymes is easy to break down the biomass or dead root that has been accumulated there.

    And, some growers use the normal water for flushing. The water is mostly the distilled water, RO water, or deionized water with a neutral PH of 7.0.


    The safety precautions always come first while using such flushing agents with plain water. It doesn’t mean that the product is secure if it is labeled as organic or natural.

    Be sure that you read the label very carefully and consider words like Warning, Caution, or Danger. You may need to wear gloves while handling those products.

    Final Words

    This is the ultimate process and understanding of how to flush hydroponic plants. Everything was defined in detail with regards to pre-consideration factors, steps, arguments ‘against’ and ‘for’ flushing the hydroponics.

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