Updated at: 10-10-2022 - By: Sienna Lewis

Once every two to three weeks is a good rule of thumb when it comes to hydroponic water changes. Consider your hydroponic system’s setup, plant development, and pH requirements before changing the water. Hydroponics may appear complicated at first, but you must understand that the lack of soil and sunshine places more responsibility on you to ensure the success of your plants.

Healthy transplants can be grown in a greenhouse and hydroponic system at the same time. Everyone may enjoy a year-round supply of food thanks to hydroponics and greenhouses, which would otherwise be impossible. There are certain drawbacks to the use of this technology, such as the frequency with which you’ll have to change its water.

How Often Do You Change Water In Hydroponics: What To Consider

Bi-weekly changing, but…

Changing your water every two to three weeks is a good rule of thumb. Changing the water on a regular basis is influenced by three factors. Before making a decision, learn about these three aspects. Just because you think it’s easy to dump and replace the water in hydroponics doesn’t mean it’s actually that straightforward.

Due to the fact that within two weeks the tank’s water capacity will be equivalent in importance to the supplied top-off water, this bi-weekly plan is recommended. The over-accumulation of nutrients in hydroponics, as well as bacteria and fungal growth, can be prevented by changing the water every two weeks. Your setup, plant development, and pH level may affect this frequency.

Hydroponic Set-up

A drawback of hydroponics, according to the University of Massachusetts Amherst, is that it requires a certain level of expertise. Because hydroponics is so different from traditional farming, you’ll have to rely on your knowledge of chemical and plant production and technology to make it work. This is one of the reasons why the way you set up your system will influence how often you change your water.

Evaporation and plant use, for example, could cause water loss in your setup more quickly. For example, many light, heat, or water tanks may be located close to these sources. If you’re utilizing a lot of plants, it means you’ll need to change out the water a lot more frequently.

How Often Do You Change Water In Hydroponics - Krostrade

Plant growth

The rate at which your plants grow determines how often you change the water in hydroponics more than the number of plants you have. In hydroponics, your plants’ efficient evaporation and transpiration will consume the water in the reservoir, resulting in a high yield and a quick growing time. In order to keep the water level stable, you must add water on a regular basis.

To maintain a constant water level, you may have heard the expression “topping off.” To keep the nutrients in the solution at a safe level, you do this gradually. Every two days or every day is a lot less frequent than changing the water.

pH requirements

Products and additives that raise and lower hydroponic pH levels are used to obtain the desired level. Even while it’s usual to see a rise in the level when you switch solutions, if you discover that the level is continuously out of range, you need to properly change your water.

Adding pH additions isn’t supposed to be a panacea for pH changes. Additionally, the pH in your garden should be within the specified ranges in order for your plants to thrive. Changing your water will provide you with a long-term remedy.

How To Change Water In Hydroponics

Hydroponics relies on frequent water changes, but the precision of your method is just as important. There are two ways you can alter the water: by refilling and by removing and reinstalling it. It is imperative that you employ these two techniques on a regular basis.

Earlier in this article, we talked about filling up your water tank. To maintain the reservoir’s capacity and prevent it from being too concentrated, you top it off with water from the name itself. Topping off can be done on a daily or weekly basis, but it’s critical to measure the amount you add so you know when to perform a thorough water change.

On the other hand, water changes would be less frequent in the long run. It’s important to keep track of how much water you add to your reservoir because if it reaches half of your total amount, it’s time to change the water.

How Your Setup Affects Frequency of Water Changes

The characteristics of your hydroponic system can also influence how often you need to replace your water. Evaporation and plant use will reduce the volume of water in your reservoir.

If you have a lot of light and heat in your setup, you’ll lose more water through evaporation. If you don’t have enough coverage on your reservoir, or if your reservoir is located close to light and heat sources, this is even more of a problem. Additionally, if you have a lot of plants or ones that require a lot of water, you’ll lose water more quickly. Adding water more frequently is a necessity if you want to produce things like irises, lettuce, or spinach.

Water reservoirs with a smaller capacity need to be replenished with fresh water more frequently than those with bigger capacity. Everything you need to know about water tanks has been included in a comprehensive reference.

Adding water to your hydroponics between water changes is a common practice. If you lose a significant amount of water, you should plan on re-filling the water tank every day. Every few days, if you don’t observe much of a difference in water levels between days, you should plan to top up the water. It is recommended that you perform a water change every two to three weeks. After gaining some experience with hydroponics, you’ll be able to establish a regular watering and partial watering plan.

How to Change Your Hydroponic Water

There are two ways to swap out the water in your hydroponic system. It’s critical to replace water in both methods, and to do it on a frequent basis. We’ll go into further depth about why this is the case later, but for the time being, you should be familiar with the two approaches and how to use them.

Filling your water tank to the brim is the first type of “water change.” There are times when you will need to refill your water supply. Using pH-balanced, purified water is the most effective method. Adding water frequently, if not everyday, is a common occurrence. Don’t forget to record the amount of water that is added when you refill the water. These logs will come in handy when it comes time to perform a larger water change.

Changes in volume of water are made much less frequently with the second sort of water change. Water changes should be performed after the reservoir volume has been increased by half, as documented in the logs.

For this, remove or drain half of the reservoir’s volume and replace it with clean, pH-balanced water (for example, if your reservoir contains 100 liters and your logs show you added 50 liters over the course of a few weeks by topping up the water), Most hydroponic systems require a larger water change every two weeks, but smaller reservoirs may require it every week to ten days more regularly. This is not uncommon.

Water Changes to Manage pH and Nutrients

Keeping your pH level stable and ensuring that your plants are getting the nutrients they need is part of the rationale for regular water changes.

Water’s pH will fluctuate over time, and you’ll notice it. The nutrients you’ve added to the water will be useless if the pH isn’t right for your plants.

We’ve put together a comprehensive guide on how to measure the pH of your water.

There are better ways to ensure your plant’s growth than simply changing the water in its entirety.

The first problem is that other substances, such as ammonia or nitrites, can build up to dangerous concentrations in your system and destroy your plants.

Second, stagnant water can become a breeding ground for germs and fungi if no fresh water is added.

Because of this, as well as roots that have been damaged by chemicals, root rot thrives in these conditions. Our root rot prevention and treatment guide will help if you’re not sure where to start.

To avoid shock to your hydroponic plants, you need numerous water changes to maintain pH rather than a single, occasional one. Maintaining a stable pH level is easier with regular additions of clean water between bi-weekly water changes.

Plants can be negatively impacted by sudden, abrupt changes in water conditions (such as when water is completely changed).

How Often Should You Change the Water in Your Hydroponic System? - Krostrade

Managing nutrient saturation

Over-saturation of minerals can harm plants, thus water changes are beneficial when adding nutrients. When plants use nutrients, they leave behind minerals and chemicals.

Plants use up more water volume than they do nutrients, which creates a situation where nutrients are more saturated than when you first added them. Too much of these leftover trace minerals can burn plant roots or kill your plants. So if you’re not sure if your nutrient levels are helping or harming, always test for it.

Testing to determine water changes

Plants use up more water volume than they do nutrients, which creates a situation where nutrients are more saturated than when you first added them. Too much of these leftover trace minerals can burn plant roots or kill your plants. So if you’re not sure if your nutrient levels are helping or harming, always test for it.

Different types of testing

Nutrients become more saturated than they were when originally provided because plants consume more water than they can replenish. Leaving too many of these trace minerals in your soil might damage or even kill your plants. So, if you’re unsure about whether or not your nutritional levels are beneficial or detrimental, it’s best to have them tested.

pH testing

pH testing are a useful tool for keeping tabs on your water’s pH (potential hydrogen concentration). The optimal pH for most plants is between 5.5 and 6.5. While the water cycle may cause this to fluctuate slightly, it should not change significantly.

If you observe any signs of wilting, illness, damage, or discoloration in your plants, you should conduct a pH test every three days or so. Paper strips and liquid solutions are both available as pH test kits. Due to the ease and precision of digital pH testing pens, they are becoming increasingly popular.

EC testing

Your hydroponic fertilizer solution’s electrical conductivity (EC) can be monitored and maintained via EC testing. While the appropriate EC level for your particular crop may vary, most plants grow at levels between 1.2 and 2.0. Your water needs more nutrients if your EC falls below that level.

You’ll also need to dilute the solution if the EC level is too high. It’s possible that you’ll need to slowly lower the level over several days by draining some water and replacing it with fresh. Digital pens are the most common way to test for EC, and some of these pens can also test for pH.

Some farmers assess their water levels every day until they get a better sense of what they’re dealing with. Every three days (when you test your pH) and every time you add nutritional solution, you should at the very least be measuring EC levels. If you’re unsure, check out our instruction on how to measure the EC in water.

Hydroponic solution changing schedule & frequency

Topping off your solution

Evaporation and transpiration cause the water level in the reservoir to drop a little bit each day as your plants grow, so keep an eye on it. Transpiration is the process through which plants breathe, causing water to evaporate from their leaves.

Adding a small amount of water to your hydroponic solution on a regular basis is the best way to counteract the loss of water in your system.

“Topping off” refers to the practice of adding water gradually to keep fluid levels stable. So why does water matter? Because nutrients like nitrogen and copper and zinc are more difficult to get out of the solution than water is. It’s also possible to harm your plant by overdosing it on certain nutrients.

Exactly how frequently you should be refueling is a matter of personal preference. It’s best to do it every two to three days, but you can do it as often as you desire. When topping off, make sure to measure out the correct amount of water.

Once you’ve added enough water to fill your reservoir to its maximum capacity, it’s time to switch out your solution completely.

The frequency and schedule of hydroponic solution changes.

Once every 10 days you’ll need to replace the entire 5 Liter reservoir if you’re adding 500mL of water each day. In the case of a 20-liter reservoir, it’s fine to wait 20 days before doing a full change.

When it comes to this, it’s best to get things down to the nitty-gritty if you can. There are many advantages to hydroponics, but it is more of a science than an art, thus care must be taken when using this method.

Perfect pH

pH is the concentration of hydrogen ions, or acidity, in a particular solution, as you may or may not recall from chemistry. This is a difficult concept to grasp, but hydroponics makes it a lot easier to grasp.

The development of your plants is not directly affected by the pH of your solution, but the ability of your plants to absorb nutrients from your solution is affected by pH. Roots can’t properly absorb those yummy nutrients if your pH is out of whack. The optimal pH range for most species is between 5.5 and 6.5, but this varies from species to species. Here are a few samples:

How to measure pH

The process of determining pH is straightforward. In addition to hydroponics supply stores, you may also find pH test sticks in pool and aquarium supply stores.

Observe how they change color after being dipped in your solution, and then check the back of the box to see what the pH is.

Checking your pH everyday, at least in the beginning, is a smart idea.

Managing pH in your hydroponic system

It’s normal for the pH to fluctuate a little while switching from one solution to the next. An upward trend is more common than a downward trend.

There are techniques to adjust your pH if you find it too high or too low for your taste. Commercial “pH up,” “pH down” products, or vinegar can be used to modify pH levels.

The pH of your solution must be precisely calibrated for optimal growth, just as you would with the water level. Adding pH-altering items to your reservoir water isn’t necessarily the best long-term answer (no pun intended). They only last a short time and don’t address the underlying cause of your solution’s pH imbalance. It will, however, require a complete overhaul of your strategy!

pH additions aren’t always effective, either.

A full water change-out may be necessary if you discover that your pH is consistently out of the normal range even after balancing it with additions.

The pH of your water might fluctuate over time, and it’s advisable to replace the water if you’re having troubles on a frequent basis.

Conducting Conductivity Tests

The electrical conductivity of your solution is one final consideration. Electrical conductivity, or EC, is a measure of how well your solution can conduct an electric current. Without getting too deep into the chemistry of it, most of the nutrients in your solution are really good at conducting electricity. Therefore, the higher your EC, the greater your nutrient concentration is.

One further thing to consider is the electrical conductivity of your solution. Your solution’s electrical conductivity (EC) indicates how well it can move a current. Your solution contains a wide range of nutrients that are excellent conductors of electricity. As a result, the higher your EC, the more concentrated your nutrient supply is.

You may alter the EC of your solution in the same way you modify your pH levels: by adding nutrients or diluting it with water. In the end, if you see that your EC is consistently having problems that can’t be addressed with modest tweaks, it may be required to replace the entire unit. Make it a point to check your EC daily when you’re just getting started with hydroponics.

Other reasons to change the hydroponic solution

A few other scenarios in which you should adjust your hydroponic solution include the following

  • In the event that you adjust your nutrient ratios You’ll need to flush out your tank if you’re making a significant alteration in the nutritional ratios in it, so you’ll need to start from scratch.
  • Chlorosis is the yellowing of your plant’s leaves.
  • The appearance of a purplish tinge in your plant, which is sometimes referred to as “purpling.”
  • Sections of a leaf or a root may die of necrosis.
  • Stunting. If a portion of your plant is growing considerably more slowly than the rest, or if the plant as a whole is developing much more slowly than usual, you should toss your solution and try something new.

Related Questions

How long does hydroponic nutrients last?

If you drain, clean, and remix your nutrients daily and top off the system with ordinary water, your hydroponic nutrients should last 7–10 days. Nutrient strength decreases as plants use up nutrients in their system.

Can you grow hydroponics without nutrients?

Yes, but the nutrients in plain water are insufficient to support healthy plant growth. Using hydroponics, you don’t have to rely on soil for plant nutrients, and you can carefully control the nutrient balance of your plants.

What can I do with my used up hydroponic solution?

A lot of work goes into making and balancing hydroponic solution; throwing out the expensive, nutrient-rich plant juice is disappointing and a little wasteful. However, there is good news: you may also show your affection to your outdoor plants! It’s a great idea to dilute the wastewater with tap water before spreading it on your flowerbed or outside garden.

Remember to flush your wastewater down the drain if you don’t have any outside plants to share with. If you flush your toilet and the flush water spills into a creek or other water source, it can have a negative impact on the ecosystem’s nitrogen balance and harm the organisms that live there.

When to Change The Reservoir Water – Hydroponics Explained

Are hydroponically grown foods as good for you as traditionally grown foods?

They’re definitely a possibility! Getting the vitamin balances just right is key. Just because a plant grows in soil doesn’t mean it has more or less nutritional value than one cultivated hydroponically. This also applies to flavor. You can get just as wonderful a flavor out of hydroponic fruits, vegetables, and herbs than you can get from a farm.

In addition, hydroponically grown plants are devoid of pesticides and other potentially dangerous chemicals that outdoor plants may be subjected to, making them a safer option.


Using hydroponics and greenhouse gardening, gardeners may grow food year-round without having to worry about space or location constraints. Hydroponics’ water-changing frequency is one of its tasks, which you should become familiar with. Typically, this is done twice a month, and the water can be topped off monthly or daily.

If you have a certain setup, plant growth, and pH requirements, you may need to replace your water more frequently. While learning about all of these variables may seem daunting at first, if you’re growing hydroponically, you’re already familiar with most of them. Remember how much water you add to the reservoir so you know when to change it out entirely.