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Boosted Water Supplies [Hardfacts]


Traditionally the majority of properties in the UK are fed with cold water from a towns main supply. Those in Southern England, apart from a kitchen sink, commonly make use of water storage tanks to feed taps while in Northern England the practice is to feed all cold water taps directly.

Boosted water supplies are found where pressure is an issue due to poor water mains pressure or the building height e.g. in medium and high rise building(s).

In these cases water is supplied from the mains supply to a small break (storage) tank in the ground or basement of the building and then boosted by an electric pump (s) throughout the property.

These are often fully packaged sets delivered to the building site for ease of installation.

Fractured Pipe Risk

With boosted water supplies there is always a potential risk of a vacuum occurring in the top of the riser pipe(s) in the building.

This can occur when the water supply is temporarily withdrawn.

Usually this is the result of one of the following:

  • Complete electrical failure to the controls of the pump booster set
  • Interruption to the water supply in to the water break tank
  • Loss of prime due to air ingress in to the suction pipe work feeding water to the booster pump - an ‘air lock'

When water is returned the sudden increase in flow, in to the riser pipe, will rapidly pressurize the partial vacuum ultimately causing a sudden stop in the liquid flow, causing a back surge. Any weak joints are likely to absorb the pressure and fail, causing flooding. Certain protection, such as gas filled expansion vessels and arrestors may be too slow or these devices may not be correctly located.


Damage to residential and commercial properties with boosted water systems is occurring and these incidents can result in wide spread damage. In residential blocks this can result in a large number of the apartments being made uninhabitable with alternative temporary accommodation being required.

The use of dry linings and laminate flooring in modern apartments often adds to the damage.

Also the resulting insurance claim can be challenging due to the various interests presented by the property owners, housing associations, private buy-to-let and tenants renting.

Key Action Steps

  • Ensure all companies and individuals engaged to work on plumbing installations are affiliated to and members of approval schemes such as the CIPHE (Chartered Institute of Plumbing and Heating) Approved Contractor Scheme and the Water Industry Approval Scheme (WIAPS) or similar schemes which are also run by some of the larger Water Authorities and are generally considered to be of similar status
  •  Have a suitably designed ‘vacuum breaker' installed by a competent contractor at the ‘top most point' of each riser pipe which is an effective method of preventing a vacuum occurring in the riser pipe of a tall building
  • Ensure the boosted pumping equipment is subject to an annual service and maintenance contract by a competent contractor
  • Carry out full commissioning tests on all new systems in their entirety, including all equipment and fittings at their working pressure, in line with equipment supplier's guidelines. A minimum commissioning period of not less than 8 hours is recommended which should be attended for its full duration.
  • Architects and property developers need to consider measures to minimise potential water damage especially when using modern methods of plumbing including these boosted water systems.
  • Residential Management Committees or managing agents need to consider an action plan to minimise the potential for water damage including damage control.

Additional Sources of Information

Aviva Hardfacts sheets - Weather and Non-Weather related damage at our Knowledge Store:

CIPHE (Institute of Plumbing and Heating Engineers) at

WIAPS (Water Industry Approval Scheme) at

CIBSE (Chartered Institute of Building Services Engineers) standards at:

HVCA Guides at:

Water Supply (Water Fittings) Regulations 2000. BS6700:2006 Design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages: specification.

Next Steps:

  • Source discounted products, available to Aviva insured customers and brokers only, via our Specialist Partners - click here to find out more about the savings you could make
  • View our Tools and Templates
  • Call our Risk Helpline on 0345 366 66 66
  •  Email us at

Please Note
This document contains general information and guidance and is not and should not be relied on as specific advice. The document may not cover every risk, exposure or hazard that may arise and Aviva recommend that you obtain specific advice relevant to the circumstances. AVIVA accepts no responsibility or liability towards any person who may rely upon this document.

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