Cleaning up in Cranleigh

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Knowle Lane Ditch

A watercourse in Cranleigh has been cleaned up thanks to months of hard work by Thames Water to trace sources of pollution in the area.


The company’s six-month investigation into pollution in the Knowle Lane ditch first began in April and has since unearthed a number of commercial and residential properties responsible for sewage, contaminated water and chemicals reaching the ditch via the surface water drains.


In total Thames Water engineers identified 17 private plumbing mistakes, known as misconnections, where waste water pipes were incorrectly linked to the surface drainage system which leads directly into the watercourse. This resulted in discharges from appliances including washing machines, hand basins, showers, baths, dishwashers and kitchen sinks flowing into the surface water drainage system, meant only for rainwater, instead of into the foul sewer network which ultimately flows to Cranleigh’s sewage treatment works.


Thames Water’s Patrick Maher, who led the investigation, said: “We know the pollution was a real concern to some people in Cranleigh, as it was to us, so we’re really pleased we’ve managed to trace it back to its various sources, and most importantly got the property owners to rectify the problems with their plumbing.


“Misconnections are private plumbing mistakes which often happen during the construction of new buildings or the refurbishment of older ones so, while the quality of the water in the ditch has significantly improved now, to keep it clean it’s vital anyone having work done at their property employs a reputable plumber and knows exactly where their waste is heading.”


During Thames Water’s 200 hour-long investigation in Cranleigh, engineers used cables with small CCTV cameras on the end to see inside the surface drainage system and also visited properties to inspect internal and external pipework. In cases where a misconnection was suspected, harmless coloured dye was poured down sinks, drains and toilets which was then traced to see whether it appeared in the surface drainage system or the foul sewer as it should have. Owners of misconnected properties were then formally instructed to rectify the issues.


Some businesses in the area were also given warnings after they were found to be pouring dirty water and chemicals directly into the surface drains.


Patrick added: “Across our whole region, plumbing mistakes can be as high as every one in ten households misconnecting waste appliances to the surface water system, which is the equivalent of over sixteen Olympic-size swimming pools of wastewater wrongly entering the waterways every single day. It’s a huge problem and by working closely with the Environment Agency to investigate reports of pollution, its one we’re doing our best to combat.”


Anyone building a new property or renovating an existing one can easily check their plumbing is properly connected by visiting an independent website called ConnectRight for step by step instructions.