How a Wates Pressure Vessel Stores Pressurized Water Using an Internal Air Cushion

A Wates pressure vessel works on the principle of separating water and compressed air inside a sealed steel tank. Instead of storing water in an open tank, the vessel uses an internal bladder or diaphragm to maintain a controlled air cushion that creates and stabilizes pressure in the system.

How It Works – Step by Step

1. Empty Vessel State
   • The tank is pre-charged at the factory with compressed air (for example, 2.0 bar).
   • Inside the vessel, the air occupies the entire volume because no water has entered yet.

1. Pump Starts and Water Enters the Vessel

1. • When the water pump starts, water flows into the vessel through the bottom connection.
   • The water fills the bladder or diaphragm chamber, pushing against the trapped air.

1. Air Compression Creates System Pressure

1. • As more water enters, the air in the top section of the vessel gets compressed.
   • Compressed air acts like a spring, storing energy and increasing the internal pressure.
   • This stored pressure is what keeps the pipeline pressurized even when the pump stops.

1. Pump Stops – Stored Pressure Takes Over

1. • When the system reaches the cut-off pressure (example: 4 bar), the pump switches off.
   • The compressed air pushes the water out of the vessel, supplying the taps, fixtures, or network without the pump running.
   • This prevents rapid on/off cycling of the pump.

1. Pressure Drops – Pump Starts Again

1. • As water is discharged from the tank, the air expands and pressure gradually falls.
   • When it reaches the pump cut-in pressure (example: 2.5 bar), the pump starts again and refills the vessel.

Why the Internal Air Cushion Is Important
Function
Benefit

Acts as a pressure buffer
Reduces pump cycling and motor wear

Maintains constant water pressure
Prevents pressure drop at fixtures

Stores usable water volume (drawdown)
Reduces energy use and pump run time

Absorbs shock and vibration
Prevents water hammer in pipework

Improves system efficiency
Extends pump and valve lifespan

Key Notes for Installers

• The air pre-charge must be set correctly before commissioning (always 0.2–0.5 bar below pump start pressure).
• If air leaks or is not maintained, the tank becomes waterlogged and loses function.
• Wates vessels use a butyl or EPDM bladder, which prevents water-air mixing and reduces corrosion risk.  For more info contact Wates Pressure Vessel Supplier in UAE or call us at +971 4 2522966.
  
  

---