The Complete Guide to Expansion Vessels

The Complete Guide to Expansion Vessels

Expansion vessels are essential components in many domestic and commercial heating and water systems. At Altecnic, we have over 35 years of experience providing high-quality, reliable heating expansion vessels and hydronic system parts to OEM’s and distributors.

From upgrading expansion vessels in commercial buildings to supplying new and replacement vessels for both new construction and existing homes, we specialise in providing durable, long-lasting components trusted by plumbing professionals throughout the plumbing industry.

In this guide we explore key information and answer common questions relating to the function, maintenance and installation of expansion vessels for domestic and commercial hadronic systems. For more information, contact our specialist team today for further advice regarding expansion vessel and component enquiries.

Content Guide:

What is an Expansion Vessel?

Expansion vessels, also known as expansion tanks, perform a crucial role in the operation of domestic and commercial heating systems. The work to maintain and regulate system water pressure for consistent operation, whilst protecting against the risk of discharging from overpressure, pipe bursts and component damage caused by fluctuations in water pressure.

This can be valuable to protect against variations in main water supply and temperature changes in closed loop heating systems which can lead to costly repairs.

How do Expansion Vessels Work?

Heating expansion vessels consist of a water storage pressure tank separated by a synthetic rubber diaphragm membrane.

The membrane forms two separate chambers, separating the system water from a pre-charged chamber of air or nitrogen gas. As the water in systems heats up, the system pressure rises, resulting in the expanded water pushing against the diaphragm, compressing the air/nitrogen gas in the chamber to accommodate for the increased water system pressure.

As water temperature decreases, the water contracts, resulting in the air or nitrogen pushing water back into the system to maintain stable levels of pressure in the system.

Components of an expansion vessel

  • Vessel Body: The main container that houses the components of the expansion vessel.
  • Diaphragm: A flexible, rubber membrane that separates system water from the air/nitrogen chamber.
  • Air/Nitrogen Chamber: A chamber containing pre-charged air or nitrogen gas to absorb pressure fluctuations from water temperature changes. At Altecnic, our range of Reflex expansion vessels are pre-charged with nitrogen to improve vessel lifespan by reducing the risk of corrosion.
  • Air Valve: Used to check and adjust air pressure during maintenance, helping to ensure optimal performance of the expansion vessel.
  • Water Inlet/outlet: The connection for the heating systems pipework, enabling for system water to enter and exit the vessel as required.

The role in Domestic & Combi boilers:

Combination boilers (also known as combi boilers) require expansion vessels to manage and mitigate the risks of the expansion and contraction of water as it changes temperature. 

Combi boilers provide both heating and hot water. As the water temperature fluctuates, water in both system loops can rise and fall in temperature resulting in excessive changes in system pressure. Expansion vessels work to stabilise water pressure protecting against excessive pressure damage to pipes, radiators and boilers which can cause costly repairs and downtime resulting in discomfort to occupants. 

As a result, expansion vessels are used extensively in heating and plumbing systems for domestic and small commercial properties, including homes, small shops, restaurants, offices and businesses. 

At Altecnic we offer a range of expansion vessels for domestic and small property plumbing systems suitable for small property boilers. For more information and support, contact our specialist team today.

The role in System and Commercial Scale Boilers

Large properties such as commercial, industrial and public buildings use large-scale system boilers to supply heat to central heating and hot water cylinders to ensure hot water availability in high volume peak demand. 

Commercial properties typically require larger expansion tanks to handle the requirements of hot water which can result in significant pressure increases due to high thermal expansion. Commercial expansion vessels regulate system pressure to prevent damage during periods of high demand and low demand.

Commercial expansion vessels are used extensively in commercial and industrial properties ranging from hotels, shopping centres, hospitals and government buildings, to offices, manufacturing plants, apartment complexes and universities. 

Contact us today to discuss your commercial expansion vessel requirements.

Expansion Vessel Installation

Guide to Selecting an Expansion Vessel

When selecting an expansion vessel for a heated water system, there are a number of key factors to consider to ensure suitability and reliable performance. These factors include:

  • System volume to Vessel Size: An expansion vessel must be fitted with sufficient capacity to accommodate for an expected expansion level of water in the heating system.
  • Maximum operating temperature
  • Static Head: The vertical distance between the expansion vessel and the highest point in the system.
  • Vessel Rating: Select a vessel with a pressure rating equal to or greater than the maximum system pressure.

At Altecnic, we supply heating expansion vessels directly to plumbing companies and independent contractors, offering an extensive range of plumbing and heating, system vessels and heat network component accessories for all plumbing maintenance/installation requirements.

What happens when an expansion vessel fails?

When an expansion vessel fails a number of negative effects can result:

  • System Overpressure
  • Inefficient Heating
  • System Noise

Common Causes of Expansion Vessel Failure:

  • Diaphragm Failure
  • Loss of Pre-charge Pressure
  • Component Corrosion
  • Physical Damage

Your Trusted Hydronic & Plumbing Component Supplier

With over 35 years of industry excellence and innovation, we supply complete hydronic and plumbing component solutions suitable for commercial and domestic applications. Our expansion vessels are backed with a comprehensive 5 year warranty.

For more information and enquiries, contact our specialist team today.