Flushing is the process of thoroughly cleaning out a hydroponics system to ensure the health of the crops that will be cultivated in it. Flushing can be done before harvest, but is only usually undertaken when the crops are showing overt signs of distress.
As was mentioned previously, flushing is one of the ways that you can remedy plant stress. Flushing helps reduce plant stress by physically removing salts in the water.
Salt build-up is a natural occurrence in hydroponics systems as the various components of liquid fertilizers actually separate once the fertilizer is applied to the water.
With the action of water and the plants themselves, some nutrients are left behind and eventually, the nutrient concentration gets higher and higher. What happens when there are too many nutrients in the water is the dreaded nutrient lock.
When nutrient lock occurs, the plants are unable to absorb and utilize the nutrients in the water and they become malnourished. Sounds paradoxical, right?
There is so much ‘good stuff’ in the water that the opposite occurs – the plants just lose the ability to absorb the nutrients.
Luckily, it is not difficult at all to remedy this situation, though it might take a little longer for your system to normalize precisely because it needs time to remove the excess salts from its pipes and reservoir.
There are actually a variety of ways that you can perform a complete flush of a hydroponics system, but below is the simplest method that gets the job done.
Feel free to add steps in between if you feel inclined to do so, but otherwise, this procedure can be considered ‘complete’ as it is.
The first step is to drain the main reservoir of your hydroponics system. If you have a conventional garden, feel free to pour the water there as it is still filled with lots of nutrients.
Drain the reservoir completely until the bottom of the vat is dry. If you are using a smaller type of system that utilizes buckets and other smaller containers, do the same – the main tub from whence the nutrients are circulated from must be emptied completely.
Once the reservoir or tub is drained, it’s time to clean it out physically. Flush it continuously with water, with the pump off and with the drain opened, so that invisible components sticking to the bottom and the walls are removed.
Excess salts are colorless, but they will cause mayhem in your system once they mix with your water again. If you have been using your hydroponics system for some time now, you may see evidence of algae on the walls of the main reservoir.
By all means, scrape off visible fungi and algae by using a plastic scraper. Manually remove as much of the gunk as possible, and flush what you are able to remove away. Do not forget to rinse everything after you scrub or scrape. It’s important that the visible pieces are removed completely from the system.
Once the system has been scraped and flushed thoroughly, close the drain of the reservoir and fill your system again with water. Turn on the pump so it begins recirculating the water again.
Use plain water for this one, but if possible at all, use purified or filtered water. Purified water is just better for cleansing hydroponics systems. This is the point where you can add an appropriate amount of flushing agent to your system.
A flushing agent usually kills bacteria, fungi, algae and other microorganisms and also helps clear the water of other impurities.
There is no general approach to applying a flushing agent – follow the manufacturer’s instructions to get the best results. It would also be helpful to match the flushing agent with the type of system that you have or the type of water that is available for use in your system.
After running the system with the flushing agent, drain everything once again and try to inspect the different parts of the setup to see if there are any leftover sediment, molds or algae. Perform another rinse if you see fit, and proceed to the next step.
This is the longest phase of the flushing process. Fill the setup again with water, making sure that you have sufficient water to reach the optimum level of water in all the vats or tubs.
You are free to add a flushing agent or not. If you are unsure, check the manufacturer’s instructions once again if you need to run the system twice with the same solution. Check the pH and EC of the water and adjust as needed. The system has to exhibit the right level of EC and pH in order to be ready. Turn on all the pumps let everything run for 24 hours straight.
After 24 hours, drain the entire setup for the last time and refill with purified water. Add the correct amount of nutrients in the nutrient reservoir and operate your setup as you normally would.
There will be no need to perform another flush unless you see problems with the EC or pH levels, or if your plants exhibit signs of nutrient lockout. In which case, repeat the process from the beginning to remove excess salts from the water.
1. It is recommended that you perform a flush a week from harvesting time, to ensure that everything is ideal in the system, including nutrient, pH and salt levels. It is imperative that these be scanned and measured on a daily basis so you can monitor for any severe fluctuations.
We also recommend using hydroponics monitoring software so you can observe trends over a period of time, so you can predict if something is going south or not.
2. Flushing before harvesting has an additional benefit: it will make your harvest taste better. Flavor is affected by the nutrient levels of the water, and balanced, purified water will definitely improve the flavor of whatever crops you intend on harvesting.
Bitter aftertastes of hydroponic crops usually means there is an overabundance of one or two nutrients in the system, and that will really manifest in the plants themselves once eaten.
3. Performing a flush just might be what the botanist will order if you see brown, curling leaves in your plants. This symptom is usually associated with nutrient lock, which can be fatal to any type of crop.
4. Generally speaking, it is better to flush with purified water than tap water. Tap water is filled with minerals and chemicals used to remove metals and bacteria from the water itself. However, these same chemicals can taint your hydroponics system and mess with its balance.
If you don’t have access to spring water for example, you can always use a large system filter to remove impurities from tap water before you use it in your hydroponics system. The purer your water, the easier it would be to balance its pH and EC levels. In the long term, this would definitely make your job easier.
5. If you are using grow media like coconut coir, which is organic and has a moderate ability to hold on to nutrients, you have to watch your crops carefully as they may experience malnutrition during flushing. Yes, we won’t be flushing and keeping your plants’ roots dry at any time during the process.
The flushing period for most grow media should also be shorter – about seven days only.
6. You can check for ripeness by observing your plants’ resin glands for changes. Resin glands will start to change color when they’re ready to be harvested.