22. October 2013 11:54
Traditionally the majority of properties in the UK are fed with cold water from a town’s 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 the 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 This can occur when the water supply is temporarily withdrawn.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 into the water break tank
- Loss of prime due to air ingress into the suction pipe-work feeding water to the booster pump, in other words an ‘air lock’
When water is returned the sudden increase in flow, into the riser pipe, will rapidly pressurize the partial vacuum ultimately causing a sudden stop in the liquid flow and subsequently a back surge. Any weak joints are likely to absorb the pressure and fail which will cause 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 does occur and these incidents can result in wide spread damage. In residential blocks this can involve a large number of the apartments which are made uninhabitable with alternative temporary accommodation being required.
The use of dry linings and laminate flooring in modern apartments often adds to the damage.
The resulting insurance claim can be challenging due to the various interests presented by property owners, housing associations, private buy-to-lets 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). Other schemes are 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 the equipment supplier’s guidelines. A minimum commissioning period of not less than 8 hours is recommended which should be attended for its full duration
- Residential Management Committees or managing agents need to consider an action plan to minimise the potential for water damage including damage control.