The delivery of safe, clean, high-quality drinking water is central to what we do. It underpins the public health of our region and is a fundamental expectation of customers.
The Drinking Water Inspectorate (DWI) measures performance at our treatment works, where we have delivered an excellent performance, with just three coliform failures compared to eight in 2016. The same is true of our storage reservoirs, which store treated water at points around the network and where we achieved 99.99% compliance this year. Both these results are due to a successful programme of work to improve the inspection process of treated water tanks and storage reservoirs. As a result, we were among the highest performing water and sewerage companies in the industry for the DWI measures of Disinfection Control and Reservoir Integrity.
We have once again exceeded our target for the quality of water travelling through our network to homes and businesses. Mean Zonal Compliance is the key measure used by the Drinking Water Inspectorate to determine compliance with the stringent regulatory drinking water standards for England and Wales. For the second year in a row we achieved 99.97%, the highest level for nine years. The number of contacts we receive from customers about the appearance, taste and odour of their water has stayed at a record low of 1.38 per thousand people for the second year running.
Our planned lead communication pipe replacement programme has continued, replacing old lead pipes with new, plastic ones to help reduce levels of lead in drinking water for our customers. There are still places in our region where lead pipes are relatively common due to the high number of older homes. Communication pipes join our water mains network to customers' private pipes.
A major plank of our efforts to protect water quality is work to reduce the amount of metaldehyde entering rivers and reservoirs. Commonly used as slug control by farmers, it is very difficult to remove from water. Slug control is essential for farmers, so our team of catchment advisors have been encouraging them to shift to an alternative product – ferric phosphate. This is more expensive and some farmers are concerned about its effectiveness, so we are now in the second year of a voluntary trial called Slug it Out, that supports farmers around our key reservoirs to switch products and see for themselves. This year we added Rutland Water to the trial area, which now includes the natural catchments around the reservoirs at Pitsford, Rutland, Ravensthorpe, Hollowell, Alton and Ardleigh. Metaldehyde levels in the trial catchments have fallen dramatically, despite remaining high in surrounding areas, while ferric phosphate has coped well in a year that saw high slug numbers.
Pesticides other than metaldehyde can also find their way into rivers, washed off farmland by heavy rain or blown there by high winds during spraying. Once in the water, they can only be removed by costly treatment processes. While use of many pesticides that cause us problems is restricted ahead of rain, winds or high temperature, farmers tell us it can be difficult to get accurate, detailed local weather information. In response we have installed 10 precision weather stations on farms across the region. The data is available to farmers through an app, giving them detailed local weather predictions for the next 10 days and a real-time forecast of spraying conditions for the next six days.
In addition to inspecting our own sites, Anglian Water's team of Water Regulations Inspectors visit thousands of commercial properties every year to check their plumbing meets the right standards. This year, the team carried out more than 9,000 inspections, including power stations and a petrochemical site, as well as schools, hospitals and care homes.
More than half of the properties we inspect fail, with people's lack of awareness about substandard plumbing and its risks being the biggest challenge. This year the Water Regulations team launched a new campaign to educate customers and communities on how to safeguard their drinking water supply.
Part of the campaign is a collaboration with colleges to deliver training and education on the regulations and make sure newly qualified plumbers carry out their work properly and understand the implications of getting it wrong. We continue to support WaterSafe, the approved plumbers scheme, and carry out regular audits of members' work to ensure continued high standards.