Expansion Vessel Servicing, Inspection & Testing
Annual expansion vessel servicing for heating systems, boilers, unvented cylinders and plant rooms across London and inside the M25. Pre-charge pressure checked, diaphragm condition assessed, vessel recharged and a written test record issued. £120+VAT per hour with a one hour minimum.
What this service covers
Expansion vessel servicing & maintenance
A full expansion vessel service isolates the vessel, drains the water side, measures the air-side pre-charge against the system design pressure and recharges it back to specification. We check the Schrader valve, the vessel shell for corrosion, the mounting bracket and the isolating valve, then refill and repressurise the system before we leave. Vessels on heating circuits, boilers, unvented cylinders and plant rooms are all covered.
- Air-side pre-charge measured and reset
- Diaphragm condition and waterlogging check
- Schrader valve, shell and bracket inspection
- System repressurised and vented after service
Expansion vessel inspection & testing
Expansion vessel testing tells you whether the vessel is still doing its job before it causes a pressure relief discharge or a boiler lockout. We depressurise the water side, apply a gauge to the Schrader valve and confirm the vessel holds its charge over a timed hold test. Any vessel that will not hold pressure has a failed diaphragm and is reported for replacement rather than repeated recharging.
- Timed pressure hold test on the air side
- Failed diaphragm identified and reported
- Sizing checked against system volume
- Photographed written inspection report
Expansion vessel pressure check
An expansion vessel pressure check is a quick, low-cost visit that catches most pressure problems early. Correct pre-charge is typically 1.0-1.5 bar on a domestic heating circuit and 3.0-3.5 bar on a potable vessel serving an unvented cylinder, but we always set to the pressures the system and cylinder manufacturer specify rather than a rule of thumb.
- Set to manufacturer pre-charge, not a generic figure
- Filling loop and PRV operation checked
- Gauge accuracy cross-checked on site
- Fault found on the day wherever possible
Annual maintenance & service contracts
Expansion vessel annual maintenance is the cheapest way to avoid weekend boiler lockouts and discharging pressure relief valves. We schedule the visit alongside your boiler or plant service and keep a record of every pre-charge reading, so degradation is visible year on year. Expansion vessel maintenance contracts are available for landlords, managing agents and multi-site operators.
- Annual or bi-annual scheduled visits
- Reading history kept per vessel
- Priority response for contract customers
- Multi-site and managing agent pricing
Expansion vessel engineer near you
Looking for an expansion vessel service near me in London? Our engineers cover all London boroughs and the surrounding M25 counties with same-day slots in most postcodes. Call 07427 826446 and describe what the system is doing — losing pressure, discharging outside, or the boiler dropping out — and we will send an engineer with vessels, gauges and a nitrogen/air charging kit on the van.
- All London boroughs and the M25 covered
- Same-day attendance in most postcodes
- Replacement vessels carried on the van
- 24/7 emergency cover for pressure failures
Related expansion vessel services
Pressure, heating and control faults often overlap — these pages cover the rest of the system.
Expansion Vessel Recharge & Repressurisation
Expansion vessel recharging service for heating, boiler and potable systems across London. We drain the water side, reset the air-…
Expansion Vessel Replacement & Repair
Replacement and repair of failed, waterlogged and leaking expansion vessels on heating systems, boilers and unvented cylinders acr…
Potable & Hot Water Expansion Vessel Servicing
Servicing, recharge and replacement of potable (WRAS-approved) expansion vessels on unvented hot water cylinders across London — i…
Commercial & Plant Room Expansion Vessel Servicing
Servicing, pressure testing and replacement of commercial heating expansion vessels in plant rooms, boiler houses and rooftop plan…
Also see our underfloor heating repair London and heating pump repair pages.
Need an expansion vessel serviced or tested?
Tell us what the pressure gauge is doing and we will send an engineer with the right vessel and charging kit.
Call 07427 826446Frequently Asked Questions
Engineer labour from £120 + VAT per hour, with a 1-hour minimum. Parts and materials are quoted separately before work begins.
What's included in Expansion Vessel Servicing
- Condition inspection of each listed asset
- Cleaning tasks agreed for the equipment type
- Functional checks of controls and safety devices
- Readings recorded against the previous visit
- Written findings, with any repairs quoted separately
How Expansion Vessel Servicing works
- 1
Agree the asset list
Tell us which units are included and how they are used.
- 2
Set the interval
Visit frequency is based on manufacturer guidance and operating conditions.
- 3
Planned visit
The engineer inspects, cleans and tests each listed asset.
- 4
Findings
Readings and defects are recorded; repairs are quoted separately.
- 5
Follow-up
Agreed remedial work is booked, and the next visit is scheduled.
Expansion Vessel Servicing prices
| Item | Price |
|---|---|
| Engineer labour | £120 + VAT per hour |
| Minimum charge | One hour |
| Parts and materials | Written quote before work starts |
| Planned maintenance contract | Quoted per asset list |
See all rates on our prices page or read why customers choose us.
Expansion Vessel Servicing: scope, checks and next steps
An expansion vessel accommodates changes in water volume. Rising pressure while heating and discharge from a relief valve can have several causes; they do not prove the vessel needs replacement.
Separate the possible causes
Pre-charge measurement requires the water-side pressure to be relieved correctly. Compare the specified charge, vessel condition, valve leakage and available expansion capacity; measuring against a pressurised water side can mislead.
Repair or replacement?
A vessel that holds its charge may need adjustment rather than replacement. A failed diaphragm, corroded shell or inadequate capacity requires a different scope. Do not adjust a safety valve to mask pressure rise.
Maintenance is not a breakdown repair
A planned visit should establish condition and identify deterioration. An existing fault may need separate diagnosis and parts. Agree which assets, cleaning tasks, functional checks and records are included, and base the interval on manufacturer guidance and operating conditions.
Details to include with your job request
Provide the vessel label, system type, cold and hot pressure readings and where any discharge appears. Do not isolate safety devices or attempt a pressure test yourself.