Water & Wastewater Treatment

WWT August 2017

Water & Wastewater Treatment Magazine

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Page 20 of 39

Getting to Grips with… sewer jetting A sewer blockage is bad news. It can prevent or reduce the flow of wastewater through the pipe causing its contents to back up underground until it eventually overflows from manholes in roads and gardens and even from toilets. Data suggests that sewer blockages result in around 4000 property flooding incidents each year in England and Wales. In the UK, blocked sewers are o en cleared using high pressure water jetting; as such, it is generally considered an emergency operation. The Knowledge Q: What is sewer jetting? A: High pressure jetting is one of the main methods used to clean drains and sewers and to clear blockages. Jetting involves water being forced along a hose and through a nozzle at high pressure. Various nozzle/water jet configurations are available, with selection depending on pipe diameter and whether the nozzle is being used to release a blockage or for general cleaning. Q: Is there a limit on the jetting pressure that can be used to clear a blockage? A: The standard BS EN 14654-1:2014 Management and control of operational activities in drain and sewer systems outside buildings, Part 1: Cleaning states that when jetting: "Maximum working pressures to avoid Sewer jeTTing Q&A www.wwtonline.co.uk | WWT | AUGUST 2017 | 21 Stuart CriSp BUsiness DevelopMent Director concrete pipeline systeMs AssociAtion (CPSA) damage will vary according to the material of the pipe, condition of the pipe and type of nozzle". In 2005, the Water research council (Wrc) published the Second Edition of the sewer Jetting code of practice. this document provides guidance on good working when using high pressure jetting equipment. The code sets out the maximum jetting pressure for pipeline materials, varying from 1500psi for brick sewers, 2600psi for plastic, up to 5000psi for concrete and clay pipelines. In theory, best practice guidance should ensure damage to the fabric of drains and sewers is avoided but, with a variation of 3500psi between the maximum jetting pressure for brick and concrete and the need to identify the pipe material prior to clearance operations commencing, there is the potential for abuse.

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