Wondering How often do You Change Hydroponic Water? Most Gardeners are Curious About the Schedule

How often do you change hydroponic water?

According to hydroponics expert Mark, “Most systems do well with water changes every 1-2 weeks, though factors like temperature and plant type affect the schedule.” 

Through years of experience, Mark has found hydroponic water changes are not one-size-fits-all. 

This guide will explain how to observe your specific garden and tailor your maintenance accordingly. 

Read on for Mark’s proven tips to ensure bountiful harvests.

Key Takeaways

Most hydroponic systems need water changes every 1-2 weeks. The frequency may vary depending on the system size, water temperature, plant type and growth stage, and nutrient concentration.

Frequency of Changing Hydroponic Water Depends on System Size and Factors

Growing plants without soil using nutrient solutions in a hydroponic system is a clever way to cultivate crops. However, one important aspect of these soilless systems is properly maintaining the water and nutrient solution that the plants feast from. 

The frequency of replacing this hydroponic reservoir water can vary depending on factors like the hydroponics system size and type, temperature, plant needs, and solution concentration (1).

By understanding how these elements affect water quality, growers can know when it’s best to change the water in their system to promote healthy plant growth. Let’s explore the key points…

Hydroponic System Size and Type

In any hydroponic system, the reservoir water carries dissolved nutrients that plants absorb through their roots. Larger systems housing many plants tend to deplete this nutrient solution faster than smaller operations. 

Ebb and flow and drip systems tailored for plenty of crops will need fresh water and nutrients more regularly, perhaps every couple of weeks. NFT and aeroponic setups, pumping solution continuously, may require weekly changes to keep plants contently fed.

  • Larger hydroponic systems with more plants require more frequent water changes than smaller systems.
  • Ebb and flow and drip systems need water changes every 1-2 weeks for most plants.
  • Nutrient film technique (NFT) and aeroponic systems require changes about once a week.

Water Temperature

Similar to our bodies, plants’ metabolic rates increase in warmer conditions. High water temperatures above 25°C cause nutrients to break down and algae/bacteria to proliferate more quickly (2). 

Gardens will likely need new reservoir water twice as often if it’s on the hot side compared to comfortably cool water below 20°C.

Warmer water leads to faster nutrient depletion and more rapid growth of algae and bacteria. It may need changes twice as often as cooler water.

Water TemperatureChange Frequency
Below 68°F/20°CEvery 2-3 weeks
68-77°F/20-25°CEvery 1-2 weeks
Above 77°F/25°CEvery 5-7 days

Plant Type and Growth Stage

Young seedlings and divisions don’t yet consume as heartily from the solution as their mature, fruit-bearing parents. Fast-growing species tend to be especially nutritious-hungry as well. It’s important to factor stage of life and variety into the fresh water schedule.

  • Young seedlings and cloners use less nutrients and need less frequent changes than flowering plants or large plants.
  • Fast-growing plants like tomatoes and cucumbers use up nutrients quickly, requiring changes once a week or more.

Nutrient Concentration

The changing procedures varies with respect to nutrient concentration level in the water which directly affects its longevity. 

Higher focus demands more speedy renewals contrary to lower attentiveness enabling longer durations like bi-weekly intervals. It’s wise to stick to the manufacturer’s mixing instructions.

  • Higher nutrient concentrations break down faster, so solution needs changing sooner. Follow mixing instructions.
  • With lower concentrations, less frequent changes, every 2-3 weeks, may suffice.

Reservoir Water Volume

Larger volumes act as a stabilization buffer, diluting wastes and keeping nutrients balanced for plants longer than smaller tanks. A 100+ gallon tank can commonly sustain itself every couple weeks, but under 30 gallons may need weekly attention.

  • Larger reservoirs hold nutrients longer since there is more dilution of wastes. Small systems may need changes weekly.
  • Over 100 gallons can often go 2-3 weeks between changes. Under 30 gallons may need changes weekly.

Growing plants in a soilless hydroponic system provides many benefits but requires maintenance of the nutrient solution reservoir. 

By considering system particulars like size, temperature, growth stage, solution makeup and water volume, smart growers can decide optimal intervals for renewing the supply of fresh water and nutrients to support continued plant well-being.

YouTube video

Credit : Joshua Rudd

Guidelines for Water Change Frequency

Growing plants without soil using nutrient solutions provides many benefits but does require careful maintain your hydroponic reservoir. 

Proper water monitoring and replenishment is key to keeping plants thriving. While hydroponic water changes needs vary, some common tips can help decide when to replace the water in different system types.

Deep Water Culture (DWC)

In deep water culture, roots are suspended in nutrient solution. From experience maintaining various DWC systems, I’ve found it best to change the water every 1-2 weeks for most plants. 

Making more frequent water replacement important in warm rooms where solution breaks down quicker. My pepper plants stayed happiest with 3 week intervals in the cooler months.

  • For most plants, replace the water every 1-2 weeks
  • Change water more often in warm rooms over 75°F/24°C
  • Extend intervals to 3 weeks if water remains under 68°F/20°C

Nutrient Film Technique (NFT)

These NFT setups I’ve used have shallow flowing water. Over time operating different hydroponic gardens, I came to learn these need the water switched out once a week to keep plants thriving. Young seedlings seem to do even better with changes twice weekly.

  • These systems have shallow flowing water so change hydroponic water once a week
  • Young clones and seedlings may need 2x weekly changes

Flood & Drain/Ebb & Flow

Larger flood and drain tables I’ve seen on farms do well replenishing the water and nutrients every 7-10 days. But in my smaller home system, every other week was sufficient based on how ph and ec levels were maintained.

  • Larger systems watering many plants should have water replacement every 7-10 days
  • For smaller setups, every 2 weeks is usually sufficient

Home Systems

Generally speaking from all my hydroponic experience, most home hobby systems can go two to three weeks between water changes. Regular monitoring of water levels and ph levels helped me best gauge when to top off with fresh solution.

  • In general, home hobby systems can go two to three weeks between changes
  • Monitor ph levels and top off with fresh water as needed

Signs It’s Time to Change

Some telltale indicators no matter the system include cloudy brown water which no longer supports proper nutrient concentration, or ph drift exceeding 0.5 units. Reduction in plant growth or seeing deficiencies also mean it’s time for a change.

  • Cloudy or algae-filled water loses nutrient concentration
  • Ph drifts by more than 0.5 units from ideal range
  • Plants show reduced growth or nutrient deficiencies
  • Loss of water from evaporation exceeds 25%

By tailoring reservoir maintenance to your individual system needs and conditions, you’ll keep plants thriving with minimal effort. Consistent water replacement lays the groundwork for healthy hydroponic gardening.

Tips for Regular Water Changes

Keeping reservoir water fresh through periodic changes is crucial to growing healthy plants in a hydroponic system. Here are some practical tips learned through experience to help you smoothly add nutrients with each regular water level top-off or change out the water.

How often do you change hydroponic water?

Test Before Adding Water

Always check ph and ec levels before filling reservoirs. This ensures any tap water or nutrients added matches your desired ranges. Instantly catching issues avoids problems down the road.

Replace Gradually for Large Reservoirs

Big tanks can be emptied and refilled all at once. But it’s less stressful on plants to do 25% changes every few days for large volumes until fully replaced (3).

Use Same Water Temperature

Prevent thermal shock by using new water similar in temp to the reservoir. Adjust as needed with room-temp, chilled, or heated water.

Clean Equipment Regularly

Siphons and tubing carrying nutrient solutions will develop algae/mineral deposits over time. Wash in a dilute bleach solution monthly to keep flow optimal.

Keep Logs

Document ph, ec, water changes and amounts added. Note any patterns in plant responses. This helps decide best frequency of water changes for your setup.

Use Rainwater When Possible

Rainwater often has a more balanced mineral content than tap, reducing the need for ph adjustments from water addition alone.

Proper water level monitoring and periodic top-offs or full reservoir swaps are key parts of caring for hydroponic plants. Staying on top of regular, careful changes yields rewards like bountiful harvests.


How often should I change the water in my hydroponic system?

For most hydroponic systems like nutrient film technique (NFT) systems or deep water culture (DWC) systems, you will want to change or replace 25-50% of the water every 1-2 weeks (4). 

This helps maintain proper nutrient and ph levels in the water reservoir and prevents root rot issues.

What factors should I pay attention to when deciding when to change my hydroponic water?

Several factors like ph level, electrical conductivity (EC), system maintenance, temperature and humidity can affect how often you need to change the water in your hydroponic garden. 

Keeping an eye on your ph meter and EC meter readings will help you determine if/when it’s time for a water change. Smaller, more frequent water changes are usually better than letting the nutrient solution go for too long without changes.

How much of the water should I change each time?

Most hydroponic growers recommend changing at least 25% of the water solution each time you do a water change for your hydroponic system. Larger water changes of 50% or more can be done, but it’s generally not necessary to fully change all of the water at once. 

Gradual, partial water changes are less stressful on the plant roots and microbial balancing in the system.

Should I change just the water or the nutrient solution as well?

It’s usually a good idea to replace both the water and the hydroponic nutrient solution when doing a tank change. The nutrient strength and balance can deteriorate over time as plants absorb nutrients from the solution and water evaporates. 

Changing to a fresh hydroponic nutrient solution helps ensure the roots have optimal nutrients available. Be sure to use the same or similar type and strength of nutrients that your plants have been growing with.

How often should changes be made for different plant types?

Some plant types like lettuce and herbs may only need water changes every 7-10 days, while plants with higher nutrient requirements like tomatoes need changes every 5-7 days. Fast growing plants like cannabis may need changes even more frequently, every 3-5 days. 

It also depends on the size of your water reservoir – smaller reservoirs will require more frequent top-offs and partial changes.

Are there signs I should look for that indicate it’s time for a change?

Keep an eye out for any signs of root rot, nutrient deficiencies or issues affecting plant growth that could point to older, stagnant water. Yellowing or dead lower leaves are common signs a nutrient or ph imbalance needs correcting with a water change. 

It’s always best to prevent problems by maintaining a consistent schedule of partial water changes tailored to your system size and plant type.


In conclusion, keeping on top of regular hydroponic water changes is one of the easiest ways to grow healthy, happy plants. As an experienced organic farmer, I’ve found that taking the time to carefully tune your reservoir maintenance schedule to your setup’s specifics truly pays off in bountiful harvests. 

Whether you opt for more frequent smaller swaps or less disturbed bigger refreshes, being observant of subtle cues from plants and solutions helps decide what works best. Replenishing nutrients and diluting buildups before problems arise prevents future hassles. 

Don’t get too caught up in rigid rules – adapt steps as temperatures, life stages and seasons shift. With a little monitoring and simple TLC, your hydroponic garden is sure to thrive for many growing cycles to come!

Let me know if you have any other questions! I’d be happy to share more tips from my years of experience with hydroponic gardening.


  1. https://thehydroponicsplanet.com/how-often-do-you-change-water-for-hydroponics/
  2. https://bsapubs.onlinelibrary.wiley.com/doi/pdf/10.1002/ajb2.1329
  3. https://thehydroponicsplanet.com/how-often-do-you-change-water-for-hydroponics/
  4. https://getgrowee.com/dwc-water-change/

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