Installation of flow through expansion vessels

Titan Mechanical is a leading provider in the water treatment industry offering a comprehensive range of services. In this expert guide, we take a look at the use of expansion vessels in pressurised hot water systems, the risk of Legionella and how to manage those risks within your water supply.

Replacing expansion vessels and remedial works

After a risk assessment of your water system has taken place, it's likely that some remedial actions may be necessary to bring your water system up to compliance.

Our wide range of remedial water services includes expansion vessel replacement, installation of drain valves, the fitting of isolation valves, and various maintenance works. At Titan Mechanical, all our remedial work is carried out by highly trained experts who meet the risk assessment requirements and industry standards.

Bacteria and expansion vessels

One of the biggest risks to water systems is the build-up of bacteria inside. Left to grow, bacteria could increase and when dangerous levels are reached could be a risk to humans. Expansion vessels have been shown to increase the risks associated with bacteria growth because when a pressurised system is running efficiently, there could be long periods without flowing water.

The UK's Health and Safety Executive have therefore released a number of recommendations to minimise this risk.

  • Expansion vessels should be located in cool places on cold pipes, close to the incoming mains water supply.
  • Expansion vessels should be mounted vertically to reduce debris becoming trapped.
  • They should be fitted with an anti-legionella valve and isolation valve.
  • Finally, vessels should be designed to reduce the water held inside and stimulate the flow.

If you have an existing water system, Health and Safety regulations state that a full Legionella risk assessment should be carried out to identify any issues and that this should be continually renewed throughout the lifecycle.

It's also important that you check:

  • The vessel is manufactured from approved materials and installed in the correct locations.
  • That the installation of flow through expansion vessel has been carried out by a certified provider.
  • The working order of all expansion vessels regularly.

What are expansion vessels?

Expansion vessels can be found in the majority of modern pressurised hot water and heating systems. Their main aim is to protect the water system from a build-up of pressure which could damage installation. Usually, expansion vessels are filled with air. If pressure builds up in the water system, the air is compressed to absorb any excess pressure, protecting the pipework and any other components. If installed properly, the vessel will fill and empty between pump runs and exchange water at regular intervals.

The risk of Legionella

Expansion vessels are very common in water heating systems and can be found in schools, offices, factories, hotels, nursing homes, and many other places. The Health and Safety Executive has stated that these vessels could potentially carry a risk of Legionella as a result of low water flow or stagnation problems. While many people believe the risk of Legionella is reduced if a water system is rarely used, little-used outlets and water systems can often present the highest risk.

In the UK, if you are an employer, or you control premises that have an expansion vessel in its water heating system, you'll need to carry out a risk assessment of the water systems that are under your control.

Do I have an expansion vessel?

The first step is to find out whether your hot water system contains an expansion vessel. It's worth noting that if you have a combination boiler, the expansion vessel is usually hidden under the cover of the boiler. In other hot water systems, the expansion vessel can often be found in a stand-alone unit away from the calorifier or water heater. They're usually a cylinder shape and coloured red.

The different types of vessel

There are a huge range of expansion vessels including flow-through types, bladder, diaphragm, and a potable water expansion vessel.

Diaphragm and bladder vessels often include a fixed and interchangeable bladder which can be made from synthetic rubber such as EPDM. These materials can harbour the growth of microorganisms including legionella.

Expansion vessels can also be found in potable water systems. This area needs particular attention as potable water systems are designed to hold water which is suitable for consumption. Potable water expansion vessels must, therefore, comply with the highest standards of hygiene and manufacture.

Why choose Titan Mechanical for your remedial works?

Strictly compliant - Titan Mechanical ensure that all Legionella remedial works are based on the requirements of BS 8558:2015 & BS EN 806 parts 1-5 and comply with The Water Supply Regulations 1999 to ensure your water system adheres to all health and safety guidance and best practice.

Experience - Our team of experts have over 50 years of combined experience, bringing a thorough knowledge of the industry and unrivalled expertise in dealing with a variety of water systems.

Additional services - In addition to the planned remedial work and water system maintenance, we also carry out tank refurbishment and tank reline services that are cost effective and completed to a very high standard.

Accredited - We are proud to have been accredited by CHAS and to be members of the Legionella Control Association (LCA).

Nationwide coverage - With a Head Office based near Liverpool, we have teams working up and down the country and have the capacity to carry out Legionella remedial works in the South and South East England, North West, Midlands, South East England, and Wales, North, North East, and Scotland.

50 years experience

Our team of experts have over 50 years of combined experience, bringing a thorough knowledge of the industry and unrivalled expertise in dealing with a variety of water systems.

Accredited in everything

We are proud to have been accredited to the highest standard for all our services. Please [visit our homepage - link] to see a full list of accreditations.

Full suite of services

In addition to the planned remedial work and water system maintenance, we also carry out [tank refurbishment and tank reline (please link to tank reline page on all pages] services that are cost effective and completed to a very high standard.

Nationwide coverage

With a Head Office based near Liverpool, we have teams working up and down the country and have the capacity to carry out Legionella remedial works in the South and South East England, North West, Midlands, South East England, and Wales, North, North East, and Scotland.

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Titan Mechanical Services deliver all works in line with current best practice and applicable British standards.

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