An NFT system in good order needs a few minutes a day and about half an hour a week. This lesson sets out that routine and then works through what to do when something goes wrong.
The maintenance routine
Daily — two minutes
- Confirm the pump is running and the film is flowing in every channel. This is the one check that is never optional.
- Glance at the reservoir level.
- Look at the plants. Wilting, yellowing or a change in colour is your earliest warning of everything else on this page.
Every two or three days
- Measure pH and adjust back to 5.8 – 6.2 if it has drifted outside 5.5 – 6.5.
- Measure EC and correct (see below).
- Top up with plain pH-adjusted water to replace what the plants have drunk.
Weekly — half an hour
- Check the pump inlet for debris and clean the filter.
- Inspect roots in two or three pots. Healthy NFT roots are white to cream, firm, and smell faintly of nothing.
- Check every channel for standing water — a sign of a blockage or a settled low spot.
- Remove dead leaves and any failed plants. Decaying material in the channel feeds pathogens.
- Check for algae and light leaks.
- Check the solution temperature at the warmest part of the day.
Every one to two weeks — full reservoir change
Top-ups replace water but not the specific nutrients plants have selectively removed, so the solution slowly becomes unbalanced even while EC reads correctly. Drain it, rinse the tank, and mix fresh. Change fortnightly at minimum; weekly if the system is heavily planted.
Between crops
Drain fully, scrub the channels, flush the lines, clean the pump, and sanitise before replanting. Carrying a pathogen from one crop to the next is a slow way to lose confidence in an otherwise good system.
Understanding EC drift
EC movement tells you what your plants are doing. Read the direction, not just the number.
| What you see | What it means | What to do |
|---|---|---|
| EC rising, level dropping | Plants are drinking water faster than they are eating nutrient — normal in warm, dry, bright weather | Top up with plain pH-adjusted water only |
| EC falling, level dropping | Plants are taking up nutrient faster than water — typical of fast vegetative growth | Top up with nutrient solution at working strength |
| EC stable, level dropping | Balanced uptake — the system is happy | Top up with solution at working strength |
| EC rising sharply in hot weather | Heavy transpiration; risk of salt build-up and tip burn | Dilute, reduce target EC by ~20%, address solution temperature |
Troubleshooting
Pump has stopped
Treat this as an emergency. The film drains within minutes and roots begin drying immediately.
- Mist the exposed root mats by hand while you diagnose. This buys you real time.
- Check power at the socket, then the RCD, then the plug and cable.
- Check the pump inlet for a blockage — root fragments and algae are the usual culprits.
- If the pump is dead and you have no spare, hand-pour solution down each channel every 30 – 60 minutes until it is replaced. This is tedious and it will save the crop.
- Afterwards, fix the underlying exposure: fit backup power, or move the pump to a 12 V solar supply. See Part 1.
pH will not stay put
- Rising steadily — usually normal nutrient uptake in a small reservoir. If it is fast, the reservoir is undersized for the plant count.
- Falling steadily — often the early sign of organic matter breaking down in the tank or root death somewhere in the system. Inspect roots.
- Swinging wildly day to day — reservoir too small, temperature swings too large, or the meter needs calibrating. Check the meter first; it is the cheapest thing to rule out.
Algae — green film on channels, pots or tank
Cause: light reaching the solution. There is no other cause.
Algae is not directly harmful to plants but it competes for nutrients, blocks pumps and emitters, and consumes oxygen overnight when it stops photosynthesising — which can crash dissolved oxygen just when roots need it. Fix it by finding and blocking the light: cover unused pot holes, replace translucent piping, use an opaque reservoir, keep the lid on. Clean the existing growth off during your next reservoir change.
Root rot — brown, slimy roots with a sour smell
Almost always caused by solution temperature above 24 °C, which both lowers dissolved oxygen and favours Pythium.
- Get the temperature down: shade the reservoir, insulate it, add volume, or move the system.
- Raise oxygen — add an air pump and air stone.
- Do a full reservoir change and clean the channels.
- Remove badly affected plants. A collapsing root mass is a source of infection for everything downstream of it.
- Consider a beneficial-microbe inoculant to occupy the root zone competitively.
Yellowing leaves
- Older, lower leaves yellowing first — nitrogen deficiency. Check EC; it is probably low.
- New leaves yellow between green veins — iron lockout. EC is likely fine; check pH, which is probably above 6.5.
- Whole plant pale, growth stalled — check the pump and the film. A plant out of contact with the solution starves regardless of what the tank says.
Tip burn — brown, crisp leaf edges on lettuce
A calcium transport problem rather than a calcium shortage. Calcium moves with water through the plant, so anything that slows transpiration to the leaf margins causes it: high humidity, poor airflow, or high EC. Improve airflow across the canopy, reduce EC, and avoid crowding.
Channel flooding or standing water
- A root mat has grown thick enough to dam the channel — thin it, or harvest.
- The outlet or return is partially blocked — clear it.
- Flow rate is too high — trim the tap back toward 1 – 2 litres per minute.
- The channel has sagged or the slope has shifted — re-level it.
Plants at the far end of a channel lagging
The solution is arriving depleted. Shorten the run, increase the flow rate, or lower the plant density in that channel. On a cascading vertical system, the lowest tier is the usual sufferer — rotate crops between tiers so no single position is always last in line.
Keep a log
Write down pH, EC, solution temperature and the date of each reservoir change. It takes fifteen seconds and it is the difference between diagnosing a problem and guessing at one. Three weeks of readings will tell you at a glance whether today's pH of 6.4 is a blip or a trend.
You have finished the series
You now have the full cycle: the principle, the plan, the build, commissioning, planting and maintenance. The fastest way to get good at this is a short first crop — plant lettuce, keep the log, and pay attention to what your particular system does.
If something in your setup does not match what you have read here, get in touch — it is usually quicker to diagnose with a photo and a couple of readings.
Basic Hydroponics Training — the full series
- Part 1 — NFT Hydroponics Explained: How the Nutrient Film Technique Works
- Part 2 — Planning Your NFT System: Space, Water, Power and Crop Choice
- Part 3 — Assembling a Vertical NFT System: Channels, Slope and Plumbing
- Part 4 — Commissioning Your NFT System: First Fill, Nutrients, pH and EC
- Part 5 — Planting Out: From Seed to Channel
- Part 6 — Weekly Maintenance and Troubleshooting for NFT Systems (you are here)
Own our wall-mounted system? Setting Up the Hydro Works Wall-Mounted NFT System gives you the build and commissioning steps for that specific unit.