Adjusting pH for Cannabis Plants A Guide

Maintaining the proper pH levels is crucial for the health and growth of cannabis plants. Here are some steps to follow:

  1. Add any nutrients or supplements to your water first, as these can change the pH of your water.
  2. Gently shake or stir your water to ensure that the nutrients are fully mixed.
  3. Test the pH using a pH pen, drops, or strips. Choose the method that works best for you.
  4. Adjust the pH by adding either “pH Up” or “pH Down” solution, depending on whether the pH is too low or too high. The goal is to get your water in the correct pH range for your growing medium.
  5. Re-test to make sure the pH is within the proper range.
  6. Water your plants with the pH-adjusted nutrient solution, or add the water to your hydroponic reservoir.
  7. For soil or soilless growers who hand-water their plants, check the pH of the runoff water to ensure that it’s within the proper range. Hydroponic growers can test a small sample from their water reservoir a few minutes later.
  8. If you need to correct a bad pH, follow the steps above to adjust it accordingly.

How much pH Up/Down should you add?

The amount of pH Up or Down you need to add will depend on the type of water you are using. Soft water requires only a small amount of fluid to adjust the pH, while hard water requires more.

For PH Down, 1 mL per gallon of water will generally reduce the pH by about 1 point. In imperial measurements, that’s 0.2 tsp per gallon (1 tsp per 5 gallons) to reduce the pH by 1 point. Note that if you’re starting with RO or soft water, you’ll likely need less PH Down than the specified amount. If you have very hard water, you may need more.

For PH Up, you’ll need to add more to adjust the pH by the same amount compared to PH Down. Depending on how hard your water is, you need to add 2-4 mL per gallon of water to raise the pH by 1 point. In imperial measurements, that’s 0.4-0.8 tsp per gallon.

When you’re adjusting the pH for the first time, you won’t know the pH of your water or how your particular nutrients and supplements will affect it. Start by adding a small amount and keep testing until you get an idea of how much you need for your tap water and nutrients. After a few tries, you’ll have a better idea of the amount you need. It’s helpful to keep track of the total amount of pH Up/Down added each time for future reference.


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