Pressure tank vs tankless booster systems

Pressure Tank vs. Tankless Booster Systems | Engineering Comparison

Choosing between a Pressure Tank (Hydropneumatic) and a Tankless (VFD) system is a core decision in MEP design. At EKG M&E Sdn Bhd, we evaluate this based on building height, peak demand, and energy targets. While traditional systems rely on volume storage, modern systems rely on digital speed control.

1. Pressure Tank Systems (Traditional Hydropneumatic)

This system operates on a "Start-Stop" cycle. A large bladder tank stores water under compressed air. When the pressure drops to a "cut-in" point, the pump runs at 100% speed until the "cut-out" pressure is reached.

• Mechanical Logic: Uses a simple pressure switch to trigger the motor.

• Best For: Low-rise buildings, sites with very intermittent water use, or budgets prioritizing low upfront costs.

Technical Pros:

• Zero Power at Idle: When demand is low, the tank provides water without starting the pump.

• Simplicity: Fewer electronic components mean easier repairs for general technicians.

• High Flow Bursts: Can handle sudden, short bursts of high demand without immediate pump activation.

Technical Cons:

• Short-Cycling Risk: If the tank loses its air charge, the pump will turn on/off every few seconds, leading to motor burnout.

• Pressure Fluctuations: Users will feel the pressure "dip" before the pump kicks in.

• Space Heavy: Requires a large footprint in the mechanical room.

2. Tankless Booster Systems (VFD Constant Pressure)

This system uses a Variable Frequency Drive (VFD) to modulate the motor's RPM in real-time. It eliminates the need for a large storage tank by adjusting flow to exactly match demand.

• Mechanical Logic: A digital pressure transducer sends continuous feedback to the VFD "brain."

• Best For: High-rise apartments, hotels, and industrial processes where constant pressure is non-negotiable.

Technical Pros:

• Constant Pressure: Maintains a "flat line" pressure regardless of how many taps are open.

• Energy Efficiency: By following the Affinity Laws, reducing speed by 20% can cut power consumption by up to 50%.

• Soft-Starts: Gradually ramps up motor speed, eliminating the Water Hammer that bursts pipes.

• Compact: Drastically reduces the mechanical room footprint.

Technical Cons:

• Electronic Complexity: Requires specialized programming (PID tuning) and MEP expertise.

• Higher Initial Cost: Sophisticated drives and sensors increase the "First Cost" of the project.

Engineering Comparison Table

The EKG Recommended Standard: The Hybrid Setup

In modern Selangor high-rise projects, we typically install a VFD Booster with a Small "Shock" Tank (2-8L).

1. Buffer: The small tank handles minor leaks without waking up the VSD.

2. Protection: It absorbs the final pressure surge when all valves close simultaneously.

3. Efficiency: It allows the system to enter "Sleep Mode" during zero-flow hours (e.g., 3:00 AM).

Is your building experiencing "Water Hammer" or high electricity bills? Contact us now for a technical audit of your existing booster set.