Hydroponics Blog
pH Drift in Hydroponics: Why It Happens and How to Stop It
Quick Answer
pH drift is normal in hydroponics. Plants absorb different nutrients at different rates, naturally pulling pH up or down. The goal is not to eliminate drift but to keep pH within your target range (5.5–6.5) through regular monitoring and small adjustments.
Why pH Drifts Up
- Plants absorb more anions (nitrate, phosphate) than cations, releasing hydroxyl ions that raise pH.
- High alkalinity (bicarbonate) in source water — very common in UAE tap water.
- CO₂ being consumed by plant roots, reducing carbonic acid in solution.
- Evaporation concentrating alkaline minerals.
Why pH Drifts Down
- Plants absorbing more cations (ammonium, potassium, calcium), releasing hydrogen ions that lower pH.
- Root exudates and organic matter breaking down.
- Ammonium-based nitrogen sources.
- Algae or bacterial activity in reservoir.
How to Manage pH Drift
- Monitor daily. Check pH at the same time each day. Early morning is most consistent.
- Adjust in small doses. Move pH by 0.2–0.3 units per adjustment. Over-correction causes swings.
- Use a pH buffer. Some commercial nutrient formulas include buffers that slow drift.
- Use RO water as base. High-alkalinity tap water (common in UAE) causes fast upward drift. RO removes bicarbonates.
- Keep reservoir sealed from light. Light triggers algae growth which destabilises pH.
UAE Specific: High Alkalinity Water
UAE tap water often has high bicarbonate alkalinity (150–400 ppm CaCO₃ equivalent). This causes rapid pH rise even after correct adjustment. If you are fighting constant upward drift and adding large amounts of pH Down, switch to RO water as your reservoir base. The bicarbonate is the cause, not your nutrients.
⚠️ Safety note: pH adjustment chemicals (pH Up — potassium hydroxide; pH Down — phosphoric or nitric acid) are corrosive. Always dilute in water before adding to reservoir. Wear gloves and eye protection. Never add concentrate directly to a small reservoir volume.