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Jetting is a critical part of operations to clear sewer blockages but care must be taken to avoid damage from high pressure hoses. With a change in British Standards BS 5911 expected to introduce mandatory tests to concrete pipes, the sector must adapt to this new reality

With an increasing number of sewer blockages caused by fat, wet wipes and other ‘unflushables’, the need for high pressure jetting to clear them is more prevalent than ever.

The rise of the fatberg – an impenetrable build-up of fat and non-biodegradable products – is a result of modern lifestyles. Diets have changed to be oilier and more people are flushing products that the sewer system was not designed to deal with, wet wipes being the biggest culprits.

According to Water UK, the trade association representing UK water companies , there are approximately 300,000 sewer blockages annually, costing water companies £100 million every year to clear them.

While public awareness has grown significantly, thanks to better education and high profile campaigns from the water utilities, the problem, particularly in densely populated cities, is unlikely to go away completely. This means sewer jetting will always have a vital part to play.

But with high pressure sewer jetting, comes another risk – pipes splitting and leaking, leading to environmental damage and potentially serious pollution. To reduce this risk, a Code of Practice giving guidance on the safe use of high pressure jetting equipment was published by the Water Research Council in 2001. This was followed up with a second edition in 2005, which set out a maximum jetting pressure for pipeline materials, varying from 1500psi (103 bar), 2600psi (179 bar) for plastic and up to 5000psi (345 bar) for concrete and clay pipelines.

So, it is acknowledged that concrete pipes are likely to withstand higher pressure than plastic, with the European standards for management and control of operational activities in drain and sewer systems EN 14654-1 (becoming EN 14654-3 after 2019) stating: “Maximum working pressures to avoid damage will vary according to the material of the pipe, condition of the pipe and type of nozzle.”

The issue is reviewed regularly, with changes to the British Standard BS 5911 for concrete pipes and ancilliary concrete products expected next year, which will introduce mandatory jetting resistance tests to concrete pipes.

As fatberg numbers increase in the UK, the sewerage pipeline sector sector needs to adapt to this new reality and explore the introduction of robust test regimes for high pressure water jetting. New test regimes can offer assurance that every concrete pipe manufactured in the UK is robust enough to undertake the level of high-pressure jetting normally needed to remove fatbergs.

Drainage contractor Lanes for Drains agreed more resistant pipes were needed in the fight against FOG.

A spokesman said: “Our teams conform to all regulations when jetting pipes but there is still always a risk of damage. Protecting the environment is a priority for us and we fully support any measure that allows us to continue to clear sewer blockages effectively, while further reducing any risk of pipe damage. However, as with everything, education is key and people need to stop abusing the drains and sewers. That’s why we have created Unblocktober, the world’s first awareness month to educate people and get them to change their habits and reduce the need to clear blockages in the first instance.”

Safe jetting limits
There has been an understanding for some time within the drains management sector that, in general, a water jetting pressure of 3,500 to 4,000psi (241 to 276 bar) is capable of breaking through blockages caused by fat and other debris.. In theory, the best practice guidance in the Code of Practice ensures that damage to pipes due to jetting is avoided. However, such risk of damage always exists.

The code advises that the pipe material needs to be identified before starting any clearance operations. There are no guarantees advice will always be followed, especially when faced with major blockages, where water jetting pressures as high as 3,000 to 4000psi (206 to 276 bar) are sometimes needed.

Some water companies realise such risk and have policies in place to ensure that the sewers they are to adopt meet specific standards and are less prone to damage.

Thames Water requires air tests for certain types of pipe to ensure that no damage was caused by jetting before adoption. Developers are recommended to consider non-polymeric components in areas where sewer air testing is expected to be hard to undertake.

Anglian Water requires adopted sewer pipes to be able to withstand 4,000psi (276 bar) jetting pressure.

Where to find the standards
BPDA keeps a keen eye on national and international standards – this ensures that our members’ customers receive the best quality products which are compliant to all relevant standards.

All British and European standards can be found here

Sewers for Adoption guidance and water industry standards can be downloaded here

The Sewer Pipes and Resistance to Jetting factsheet is available here [BOX OUT]

For more information on Unblocktober, go to

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