Expansion Vessel Servicing, Inspection & Testing

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 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

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

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

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