Case study 1 – cross connection with a public supply

In April 2015, a Regulation 9 supply near Salisbury was risk assessed by the local authority. During the risk assessment, it was discovered that there was also a metered mains water supply connected to the private water supply network. This enables the use of mains water when there are problems with maintaining pressure on the private water supply. Supplies can be manually swapped by a switch in the pump house. This is operated through an informal arrangement with a local plumber.

The source consisted of a well in a shed (see Figure 9). The untreated supply fed a nearby property as well as another property and a farm which owns the supply. The supply was sampled for the first time in March 2015 when a sample taken at the time of the assessment was found to contain 77.4mg/l nitrate, in breach of the Regulations, and 15 coliforms/100ml.

Figure 9: Well in shed (covers removed)

Figure 9: Well in shed (covers removed)

Figure 10: well cover consists of a number of wooden planks. The chamber cover is not lockable, watertight, made of a suitable material or vermin proof.

Figure 10: well cover

The local authority promptly issued boil water advice pending an investigation into the likely cause of the presence of coliforms. They subsequently provided advice to the consumers of the supply that, although there was no concern to adult health at the levels of nitrate found, they should not supply the water to infants, and that the local authority would revisit to continue investigating the source of the nitrate. The investigation into the presence of coliforms concluded that the condition of the headworks was poor and a potential route for contamination.

The local authority raised the matter with the local water company three weeks later, during a planned liaison meeting. The water company visited the property the next day in order to fit a non-return valve to the mains water supply feeding the farm to prevent any backflow. A fittings inspection was also arranged and undertaken which confirmed the existence of a cross connection between the mains and private supplies. It was also found that the pump for the private supply was broken and the properties were being supplied by the mains supply.

The local authority, through discussion with the owner, took informal action to resolve the situation, giving him two months to carry out remedial work to mitigate risks associated with the well headworks. The well headworks was located in a shed at ground level with only old and rotten planks of wood covering the well. The cover was not lockable and did not prevent animal or surface water ingress. The private supply was permanently disconnected in February 2016.

There was some uncertainty about whether the consumer was being supplied by a private or a public supply at the time of the original sample, so the water company issued advice to boil the water, some three weeks after the local authority had, and the day after fitting backflow protection in the form of a non-return valve. All bacteriological sample results were subsequently shown to comply with regulatory standards. In January a fittings inspection was undertaken which confirmed that the contraventions had been rectified and that the two affected properties were now connected to mains water. Following satisfactory sample results the boil advice was rescinded. This case highlights the importance of effective liaison between local authorities and water companies to ensure that risks to consumers where both mains and private supplies exist are identified and resolved in a timely manner. Although, in this case, the local authority did inform the water company of the cross connection, it took three weeks for this to happen. The Water Fittings Regulations are enforceable where cross connections with mains supplies exist and when the water company were informed, they acted quickly to undertake a fittings inspection and install a non-return valve on the customer pipework to protect the wider distribution network from the risk of contamination by the private supply.

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