The GW Water Quality Report 2018 showed that 99.91% of the 6,741 analyses undertaken during last year met all national and European Union standards for drinking water – an increase on the 99.85% of 2017.
Samples were taken from three operational treatment works, three service reservoirs, the water tower and customers’ taps.
Water quality risk manager Margaret McGuinness said there was a big debate over whether 100% compliance was possible.
‘There’s always going to be something and because we take sampling from people’s taps anything that comes up, even if proven to come from the property, will still get counted,’ she said.
In total GW provided 4,526 megalitres of water to customers last year, over four times the volume of St Saviour’s reservoir.
Mrs McGuinness said one thing that was new for 2018 was a UV disinfection system at Juas reservoir.
‘UV disinfection means you don’t have to put so much chlorine in,’ she said.
When chlorine is added to water it can react with organic matter and produce disinfection-by-products such as trihalomethane – an environmental pollutant.
A small amount of chlorine is put into water after UV light treatment because, although UV disinfects water at the time, it does not carry any long-term protection.
Last year there was one THM failure compared with seven in 2017.
‘Last year we also changed the way water flows around the systems so it moves faster and by-products are less likely to build up,’ said Mrs McGuinness.
‘People can get chlorine tastes, so this improves the taste of the water.
‘One of our aims is to be the water of choice on island.
‘We supply 1,000 litres of water for 99p, if you bought the equivalent in bottled water you would be paying at least £500 and have all the plastic bottles.’
Mrs McGuinness said they are encouraging islanders to switch from bottled to tap water through Refill Guernsey, in line with the UK initiative.
Businesses that display the Refill logo will fill up water bottles for free.
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