Best Guide: What Is the Correct Startup Sequence for an Industrial RO System?| Insights by AQUALITEK

Introduction

Industrial reverse osmosis systems rely on precise pressure control and gradual flow increase. The RO membrane is a delicate, high-performance component that must be protected during startup. If the high-pressure pump is started blindly without proper preparation, it can cause irreversible damage to the membrane, piping, and seals.

To avoid costly downtime and equipment failure, it is essential to follow the correct RO startup sequence.

1. Pre-Startup Checklist (Before Turning On Any Pump)

Before starting the system, the operator must confirm:

✅ Feed water source is available and stable
✅ All inlet and outlet valves are correctly positioned
✅ Electrical connections are secure
✅ Chemical dosing systems are ready (if required)
✅ No air trapped in pipes or pressure vessels
✅ Pretreatment system is functioning normally
✅ Pressure gauges and flow meters are operational

Skipping this step can cause pressure spikes or dry-running damage.

2. Correct Startup Sequence for an Industrial RO System

The correct startup sequence is designed to gradually move water through the system while protecting the membrane.

Step 1: Start the Pretreatment System

Begin by turning on:

•Multimedia/sand filters

•Activated carbon filters

•Softener or UF system

This ensures clean, conditioned water is supplied to the RO unit.

Step 2: Start the Feed Pump

The feed pump pushes low-pressure water into the RO system. At this stage:

•Pressure is still low

•Flow is stable

•Air is flushed out

•Membrane remains protected

Let water flow for 3–5 minutes to stabilize pressure.

Step 3: Open Concentrate (Reject) Valve Fully

This reduces back pressure on the membrane and prevents instant high-pressure impact.

✅ Always start with low back pressure
✅ High concentrate flow helps flush contaminants

Step 4: Slowly Start the High-Pressure Pump

Now and only now, start the high-pressure pump. If the system includes a VFD (variable frequency drive), increase pressure gradually.

Normal pressure increase time:
⏱ 30 seconds to 2 minutes

This protects the membrane surface from hydraulic shock.

Step 5: Adjust Flow & Pressure to Operating Setpoints

Finally:

•Adjust the concentrate valve

•Set the system to the designed operating pressure

•Check product and reject flow

•Monitor TDS and conductivity

The system is now running normally.

3. What Happens If You Start the High-Pressure Pump Directly?

Starting the high-pressure pump without proper preparation can be disastrous.

Potential consequences include:

❌ Membrane cracking due to sudden pressure shock
❌ O-ring and seal damage
❌ Burst RO pressure vessels
❌ Pipe and connector leaks
❌ Instant fouling due to unfiltered water
❌ Motor burnout from dry running
❌ Water hammer effect
❌ Voiding of manufacturer warranty

Even a single incorrect startup can shorten membrane life by months or years.

4. Safety & Best Practices for RO Startup

✅ Always follow standard operating procedures (SOP)
✅ Use soft-start or VFD systems
✅ Install pressure protection switches
✅ Train all operators properly
✅ Keep an RO startup checklist posted at site
✅ Use automatic PLC startup if available

A well-designed startup procedure can increase membrane lifespan by 30–50%.

5. Manual vs Automatic Startup Systems

For large industrial plants, automatic startup is strongly recommended.

Conclusion

The correct startup sequence for an industrial RO system is essential for protecting equipment and ensuring stable performance. Always start from pretreatment → feed pump → low pressure flow → gradual high pressure.

Never start the high-pressure pump directly, as it may lead to severe equipment damage, costly repairs, and long-term operational problems.

Following this best practice will ensure durability, efficiency, and safe RO system operation.