Pressurisation Unit Maintenance Checklist
A maintenance and servicing checklist for pressurisation units covering pressure settings, pump operation, expansion vessel checks, and fill valve inspection — essential for sealed heating and cooling systems.
What is a pressurisation unit maintenance checklist?
A pressurisation unit maintenance checklist is a structured list of the 15 preventive maintenance tasks — covering visual, functional, safety and record-keeping checks — that keep a pressurisation unit running safely and reliably. It groups routine checks by frequency, from daily inspections to annual servicing, so FM teams and building engineers can plan and evidence preventive maintenance.
Core pressurisation unit checks
- Check the fill valve and strainer for blockages, scale or leaks
- Check system pressure is within the set range on the pressure gauge (cold and hot)
- Verify the pressure relief valve operates freely and is piped to a visible safe drain
- Record system pressure (cold/hot), make-up water consumption, alarm test results and any adjustments
What is a pressurisation unit?
A pressurisation unit maintains the correct static pressure in a sealed heating or cooling system. It automatically adds water to compensate for minor losses and adjusts pressure as the system temperature changes. The unit typically includes a small pump, a pressure vessel, pressure switches, a fill valve, and a pressure gauge. Correct system pressure is essential to prevent boiling, cavitation, and air ingress.
In commercial buildings, pressurisation units are usually mounted in the plant room close to the boilers or chillers they protect. They draw from either the mains cold water supply via a fill valve, or — on systems where the system water is treated — from a break tank with an integral pump. The expansion vessel absorbs the volumetric change of the system water as it heats and cools, keeping the static pressure within the band set by the high-pressure and low-pressure switches.
From an FM perspective, the pressurisation unit is one of the few assets where the make-up water meter is the single most useful diagnostic. A rising trend means a leak somewhere in the system, even if no fault has yet been raised — and catching that early avoids the much larger cost of corroded pipework and failed valves further down the line. The most common service findings cluster around failed expansion vessel bladders, fill valves stuck open, and pressure switches drifting out of calibration.
Typical Pressurisation unit maintenance checklist
A practical starting point for planned preventive maintenance. Always refer to the manufacturer's O&M manual and site-specific requirements.
Visual Checks
- Check the fill valve and strainer for blockages, scale or leaks
- Inspect pipework, unions and gauge tappings for leaks or weeping joints
- Verify the break tank level, ball valve operation and overflow path (where fitted)
- Inspect pump shaft seal for weeping or visible drips
Functional Checks
- Check system pressure is within the set range on the pressure gauge (cold and hot)
- Verify the pressurisation pump starts and stops at correct pressures (test by dropping pressure)
- Test the low-pressure and high-pressure alarm functions and BMS notification
- Inspect the pressure vessel pre-charge with a tyre gauge at the Schrader valve
- Check the expansion vessel bladder by tapping — water in the gas side indicates failure
- Check the water meter reading and trend make-up water consumption
- Check pump motor current against the data plate FLA
- Verify isolation valves on the unit operate freely and seat tight when closed
Safety Checks
- Verify the pressure relief valve operates freely and is piped to a visible safe drain
- Test the air gap and category 5 backflow protection on the mains feed (where applicable)
Record Keeping
- Record system pressure (cold/hot), make-up water consumption, alarm test results and any adjustments
Typical maintenance frequency
Suggested intervals for pressurisation unit maintenance. Actual frequencies should follow manufacturer guidance and site-specific risk assessments.
Weekly
- •Check system pressure gauge reading
- •Visual check for weeping joints
Monthly
- •Record make-up water meter reading
- •Trend make-up consumption against baseline
Quarterly
- •Test alarm functions
- •Check fill valve and strainer
- •Cycle the pressurisation pump on test
Every 6 Months
- •Expansion vessel pre-charge check
- •Pump current and seal inspection
- •Backflow protection test
Annually
- •Full service including expansion vessel pre-charge top-up
- •Pressure relief valve manual test
- •Review make-up water consumption trend year-on-year
- •Calibration check on pressure switches
Common faults and issues
Issues to be aware of when maintaining pressurisation unit equipment.
Safety and compliance notes
Key safety considerations for pressurisation unit maintenance. This is general guidance only — always follow OEM instructions, statutory requirements, and your organisation's safe systems of work.
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