Understanding pH and EC in Hydroponics
If you’re growing in hydro, two numbers will make or break your results: pH and EC. They’re not complicated, but you do need to understand them. Most of the problems people bring into our Sunshine Coast shop come down to one of these being off.
Here’s a plain-language breakdown of what they are, why they matter, and how to keep them in the right range.
What Is pH?
pH measures how acidic or alkaline a liquid is. The scale runs from 0 to 14. Zero is extremely acidic (think battery acid). Fourteen is extremely alkaline (like bleach). Seven is neutral, right in the middle. Plain water sits around 7.
When you mix nutrients into water, the pH changes. Different nutrients push the pH up or down. Your tap water also has its own starting pH, which varies depending on where you live. On the Sunshine Coast, tap water tends to sit around 7.0 to 7.5.
Why does this matter for your plants? Because roots can only absorb nutrients within a certain pH range. Think of it like a locked door. The nutrients are on one side. The plant is on the other. pH is the key. If it’s in range, the door opens and the plant eats. If it’s out of range, the door stays shut. The nutrients sit right there in the water, unused.
That’s called nutrient lockout, and it looks exactly like a deficiency. Yellow leaves, slow growth, weird spots. The food is there. The plant just can’t get to it.
What Is EC?
EC stands for electrical conductivity. It measures how much dissolved stuff is in your water. In hydroponics, that “stuff” is mostly your nutrients.
Pure water has an EC of zero (or close to it). When you add nutrients, the EC goes up. The more you add, the higher it reads. So EC tells you how strong your feed is.
You might also see nutrient strength measured in PPM (parts per million) or TDS (total dissolved solids). They’re related to EC but use different scales. We recommend working in EC because it’s consistent across meters and brands. Most feeding charts use EC.
One thing worth knowing: EC doesn’t tell you what’s in the water, just how much. It can’t tell the difference between calcium, potassium, or salt from your fish and chips. It’s a total reading. That’s why following a reliable feeding chart matters. The EC number only makes sense when you know what went in.
Why Both Matter for Your Plants
pH and EC work together. You can have the perfect nutrient strength (EC) but if your pH is wrong, the plant can’t absorb half of it. And you can have perfect pH but if your EC is too high, you’ll burn the roots. Too low and the plant starves.
Getting both right is the single most important skill in hydroponics. It takes maybe five minutes per day once you’re in the habit. And it prevents the vast majority of problems that new growers run into.
We’ve been saying this to customers for 35 years: if your plants look sick, check pH and EC first. Nine times out of ten, that’s where the answer is.
Ideal Ranges
Most hydroponic plants do best in these ranges. There are exceptions for specific crops, but these work as a general starting point.
pH
- Hydroponic systems (DWC, NFT, drip, ebb and flow): 5.5 to 6.5
- Coco coir: 5.8 to 6.2 (slightly tighter range)
- Soil (for reference): 6.0 to 7.0
It’s normal for pH to drift a bit between feedings. A small swing within the range is actually fine because different nutrients get absorbed at different points on the pH scale. A gentle drift from 5.8 to 6.2 means your plant gets a bit of everything.
EC
- Seedlings and clones: 0.4 to 0.8 EC
- Vegetative growth: 0.8 to 1.6 EC
- Flowering/fruiting: 1.6 to 2.5 EC
- Late flower (heavy feeders): up to 2.8 EC, but watch for tip burn
These are starting points, not gospel. Some plants are light feeders (lettuce, herbs). Some are heavy feeders (tomatoes, peppers). Your feeding chart will give you specific targets for each stage. Check out our nutrient guide for brand-specific advice.
Quick Reference Table
| Growth Stage | pH Range | EC Range |
|---|---|---|
| Seedlings / Clones | 5.5 to 6.0 | 0.4 to 0.8 |
| Early Veg | 5.5 to 6.2 | 0.8 to 1.2 |
| Late Veg | 5.5 to 6.5 | 1.2 to 1.6 |
| Early Flower | 5.5 to 6.5 | 1.6 to 2.0 |
| Peak Flower | 5.8 to 6.2 | 2.0 to 2.5 |
| Flush | 5.8 to 6.0 | 0.0 to 0.4 |
How to Measure pH and EC
You’ll need a pH meter and an EC meter. Some units measure both. Either way works. The important thing is that your meters are accurate and calibrated.
Types of Meters
- Pen-style meters. Small, handheld, affordable. Good for everyday checking. You dip the probe into your solution and read the screen. We stock Bluelab, HM Digital, and others.
- Combo meters. One device that reads pH, EC, and sometimes temperature. Handy if you don’t want to carry two pens around.
- Continuous monitors. Sit in your reservoir and give you a constant reading. Great for larger setups or if you want alerts when something drifts.
Whatever you buy, spend the money on something decent. A cheap meter that reads 0.5 off on pH will cause you more problems than it solves. You can browse our meters and testing range to see what’s available.
Calibration
Every pH meter drifts over time. That’s normal. You fix it by calibrating with buffer solutions (usually pH 4.0 and pH 7.0). Most meters walk you through it. Do this at least once a month, or weekly if you’re using your meter daily.
EC meters need calibration too, but they tend to drift less. A 1.413 EC calibration solution is the standard. Again, once a month is usually enough.
Store your pH meter in storage solution (or at least pH 4.0 buffer), not in plain water and definitely not dry. The probe has a glass electrode that needs to stay wet. Let it dry out and it’s toast.
What Happens When pH or EC Is Wrong
Knowing the symptoms helps you catch problems early.
pH Too High (Above 6.5)
Iron, manganese, and boron become unavailable. You’ll see yellowing between the veins of newer leaves (interveinal chlorosis) and slow, stunted growth. The plant looks pale and hungry even though you’re feeding it.
pH Too Low (Below 5.5)
Calcium and magnesium get locked out. Expect brown spots on leaves, curling tips, and brittle stems. In severe cases, root damage. Low pH also makes toxic elements like aluminium and manganese more available, which adds to the problems.
EC Too High
Nutrient burn. The classic sign is brown, crispy leaf tips. If it gets worse, entire leaf margins turn brown and curl. The roots can also get damaged. Plants in an overly strong solution will drink less water, which makes the EC climb even higher. It’s a bad cycle.
EC Too Low
The plant is hungry. Growth slows down. Leaves turn pale green or yellow, starting from the bottom (older leaves) and working up. The plant will start cannibalising its own lower foliage to feed new growth.
How to Adjust pH
After mixing your nutrients (always mix nutrients first, then adjust pH), test the solution. If it’s outside your target range, adjust it.
- pH too high? Add pH Down (phosphoric acid is the most common). A tiny amount goes a long way. Add a few drops, stir, wait a minute, and test again. Don’t dump it in.
- pH too low? Add pH Up (potassium hydroxide). Same approach. Small amounts, stir, retest.
Important: always add nutrients to your water first, then adjust pH. Nutrients change the pH, so if you adjust pH on plain water and then add nutrients, you’ll have to do it all over again.
If your pH swings wildly every day, something else is going on. Could be your water source, algae in the reservoir, or root problems. Don’t just keep chasing the number. Figure out what’s causing the swings.
How Often Should You Check?
- Every time you mix a fresh batch of nutrients. No exceptions.
- Daily in recirculating systems (DWC, NFT, ebb and flow) where the same water goes past the roots repeatedly. pH and EC will drift as the plant feeds.
- Every second day in run-to-waste systems (coco drip). Since you’re feeding fresh solution each time, there’s less drift. But checking your runoff EC helps you know what’s happening in the root zone.
- After any change. Added nutrients? Check. Topped up the reservoir with fresh water? Check. Swapped to a new stage of feeding? Check.
It becomes second nature fast. Mix, test, adjust, done. Five minutes. The growers who have the best results are the ones who check consistently, not just when something looks wrong.
Putting It All Together
pH and EC are the foundation of hydroponic growing. Once you understand these two numbers, everything else gets easier. Nutrient deficiencies make sense. Feeding charts make sense. Troubleshooting becomes straightforward instead of a guessing game.
Grab yourself a decent meter (or a combo unit), keep some calibration solution on hand, and build the habit of testing every time you touch your reservoir. Your plants will thank you with faster growth and bigger harvests.
If you’re just getting into hydroponics, head over to our beginner’s guide for the full picture. Or if you’re ready to pick up a meter and some pH solutions, check out our meters and water testing range.
Got questions? We’ve been helping growers on the Sunshine Coast since 1990. Give us a call or drop into the shop and we’ll sort you out.