RO Plant Low-Pressure and Pressure-Drop Troubleshooting
“Low pressure” can describe several different faults: low feed pressure, insufficient high-pressure pump discharge, excessive pressure loss through pretreatment or increased pressure drop across a membrane stage. Identify where the pressure changes before adjusting equipment.
First record the operating conditions
Note feed temperature, feed/product conductivity, feed flow, permeate flow, reject flow and pressures before and after filters and membrane stages. Compare readings at similar production conditions.
Common causes
| Observation | Possible causes | Initial checks |
|---|---|---|
| Low pressure before the high-pressure pump | Low tank level, closed valve, blocked strainer, undersized line or weak feed pump | Tank level, valves, suction restriction and feed-pump condition |
| Large loss across cartridge filter | Loaded, collapsed or unsuitable cartridge | Upstream/downstream gauges and cartridge condition |
| Low high-pressure pump discharge | Air ingress, rotation error, worn pump, VFD setting or electrical issue | Priming, rotation, frequency, voltage and pump curve |
| Increasing membrane-stage pressure drop | Particulate, biological or organic fouling; telescoping or flow obstruction | Pretreatment, SDI/turbidity trend, stage readings and inspection |
| High pressure with low permeate flow | Scaling, fouling, cold feed water or restricted permeate path | Normalised data, water chemistry and valve positions |
Safe troubleshooting sequence
- Verify gauge accuracy and units.
- Check tank levels, valve positions and obvious leaks.
- Inspect pretreatment pressure loss and cartridge filters.
- Confirm pump priming, rotation and electrical settings.
- Compare stage pressures and normalised membrane performance.
- Review dosing, recovery and feed-water analysis.
- Clean membranes only with a compatible procedure based on the suspected foulant.
Do not compensate blindly
Increasing pump pressure or closing the reject valve can hide the cause, increase scaling risk and damage equipment. Never exceed component or membrane operating limits. Isolate electrical and pressurised equipment before service and use qualified personnel.
ABHIRO supplies industrial RO spares, instruments and replacement membranes. For troubleshooting, share a complete pressure-and-flow log rather than only the plant capacity.
