How to measure pH and EC in growing mediums

Growers measure the EC of their container media to estimate whether the plants are receiving an adequate amount of fertilizer salts, and they measure pH to determine whether the nutrients present in the medium are in a form that roots can easily absorb.

Understanding what happens in the root zone is essential for healthy plant growth. While some pH and EC meter probes can be inserted into soil or growing media, their accuracy depends heavily on moisture levels, contact with the substrate, and probe design. 

This often results in inconsistent or misleading readings. A more reliable way to assess root-zone conditions is to extract a small sample of the solution held inside the pot. 

The PourThru method provides a simple, standardized, and non-invasive way to do this at home.

The PourThru Method for testing container media

This technique involves pouring a small amount of clean water onto the surface of the container. The added water pushes out some of the nutrient solution from the root zone, which drains through the holes at the bottom of the pot. That runoff is called leachate, and it’s what you’ll use to test pH and EC.

This method is simple and non-invasive, since you can take readings without disturbing the roots or removing any of the growing medium.

PourThru method step by step

• Water the container normally until it’s fully saturated (a few drops should drain from the bottom).
• Wait about one hour for excess water to drain.
• Place a saucer under the pot.
• Pour enough distilled or deionized (DI) water on top to get about 50 mL of leachate from the bottom.
• Calibrate your pH and EC meters.
• Measure the pH and EC of the collected leachate.

Amount of distilled water to apply to the container surface to obtain 50 mL of solution extract for the PourThru method

Container size (L)	Water to add (mL)
0.5 L	75 mL
1 L	75 mL
3 L	120 mL
5 L	200 mL
7 L	250 mL
10 L	300 mL
15 L	400 mL
20 L	500 mL

PourThru EC ranges by stage:

Development Stage	PourThru EC (mS/cm)
Early Vegetative	1.0 – 1.5
Late Vegetative	1.5 – 2.0
Peak Flowering	2.0 – 2.5
Pre-Harvest	1.5 – 2.0

Interpreting your EC and pH readings

These values are general guidelines, and every grow is different, so the key is making sure your readings don’t drift too far outside the recommended range.

Ideal range for cannabis:

• pH: 5.5–6.5
  
• EC: Depending on plant stage and nutrient source

Nutrient solubility in container media

The chart below shows how nutrient solubility changes across different pH levels in container media. Each band represents how easily a nutrient dissolves and becomes available for root uptake. The highlighted zone (pH 5.5–6.5) marks the range where cannabis can absorb most nutrients efficiently, helping prevent both deficiencies and toxicities.

Common problems caused by pH imbalances in container media

Low pH (<5.5): Micronutrients such as iron, manganese, zinc, and boron become highly soluble when the pH is low and can reach toxic levels. 

A common example is iron toxicity, which causes leaf bronzing and black leaf spots.

High pH (>6.5–7.0): Nutrients such as phosphorus, iron, manganese and zinc become harder for roots to absorb, leading to deficiencies.

High soil pH (pH > 7.2) causes iron to become bound in the medium and not available for the plant to absorb, leading to iron deficiency, which typically shows as yellowing that begins on the youngest leaves first.

Common problems caused by EC imbalances in container media

Low EC: A low EC means your plants aren’t getting enough nutrients. They may grow more slowly, and the leaves can start changing color. 

The most common early sign is yellowing of the lower leaves, which usually indicates a nitrogen deficiency.

High EC: Salt buildup can occur for several reasons: applying more fertilizer than the plant can use, starting with a medium that already contains high salt levels, irrigating without adequate leaching (runoff), or using a water source naturally high in dissolved salts such as bicarbonates, calcium, chloride, magnesium, sodium, or sulfates. When salts accumulate, they can damage plant tissues.

Symptoms usually begin on the lower leaves, showing as yellowing (chlorosis) or browning (necrosis) that starts at the leaf edges and moves inward.

High salt levels can also cause root-tip dieback, and plants may wilt even when the medium remains moist.

Elevated salinity has additionally been linked to a higher incidence of Pythium root rot.

Note: Some fertilizer brands promote very high EC levels, claiming faster or stronger growth. While that can work in perfectly controlled environments, it’s risky for beginner home growers. If you choose to follow those programs, stick to their methods exactly, the same medium, watering frequency, and runoff percentage. Any deviation can quickly lead to nutrient burn, salt buildup, or root stress.

Keeping both values in this range helps your plants absorb nutrients efficiently and avoid most nutrient-related issues.

Conclusion

Monitoring EC helps growers understand whether their plants are receiving the right amount of fertilizer salts, while tracking pH is essential because it determines how easily roots can absorb those nutrients. Together, pH and EC provide a clear picture of root-zone health and are key to preventing most nutrient problems.

The PourThru method is one of the most reliable ways for home growers to monitor what’s really happening around the roots. 

Instead of guessing or relying on inconsistent in-soil measurements, PourThru gives you a clear snapshot of pH and EC in the zone that matters most for nutrient uptake. 

By repeating this test monthly or weekly (if needed), especially in peat or coco-based media, you can detect pH drift, salt buildup, or nutrient shortages before they affect your plants.

With consistent monitoring and small adjustments, maintaining a stable root-zone environment becomes much easier, helping growers avoid common problems and supporting stronger, healthier growth from seed to harvest.

If you want to get the most accurate readings and use your meters correctly, make sure to read our guide on how to use and calibrate pH and EC meters. Learning to maintain your tools is just as important as taking the measurements themselves.

How to use, calibrate and store pH and EC meters

Register the pH and EC of your nutrient solution and runoff in your Growlog within the Grow with Jane app. Tracking these readings over time helps you spot issues early and understand what caused them!