A family has been using bottled water for more than four months while scientists have been investigating unexplained debris in their water supply.

Annie and Phil Graham-Norgan, from Par in Cornwall, discovered particles in their tap water after the pressure suddenly dropped. They said South West Water carried out tests that showed the pH level of the water was above the standard limit.

It added: "Follow-up sampling at the property and across the wider network has confirmed satisfactory water quality and has not identified any ongoing water quality concerns."

The couple said they were originally connected to an old Victorian water supply but had paid South West Water almost £6,000 to be connected to the mains to improve the water pressure three years ago.

But in December last year they discovered a problem with the new supply.

Mrs Graham-Norgan said: "It was around Christmas time last year, the flow coming out of the kitchen tap was getting less and less, and we couldn't work out what the problem was.

"Since then we've discovered there were particulates in the water - there were little bits of debris in the water that was blocking all the taps that had filters on them."

She said South West Water tested the supply and discovered it had a pH level of 10 which is above the Drinking Water Inspectorate's regulatory standard range of 6.5 to 9.5.

She also said an engineer had to replace the heat appliance on their boiler as it was full of debris.

"I've lost confidence in drinking the tap water completely," said Mrs Graham-Norgan.

Mr Norgan said the water firm had not explained what the particles were but its report had listed a "wide variety of materials".

"They haven't explained what they are, the quantities and how they affect us," he continued.

South West Water said initial sampling had identified elevated pH levels at the property which were "quickly investigated".

"The most likely cause was identified as water moving more slowly through a section of pipe serving the property," a spokesperson said.

"When water remains in a pipe for longer periods, this can sometimes affect its characteristics, including pH levels.

"In response, we flushed the local network, replaced pipework serving the property and undertook further network improvements."

They said the firm also provded bottled water "as a precautionary measure".

"Based on the findings available, we are satisfied that the water supply is suitable for daily use," they continued.

The Drinking Water Inspectorate said: "The regulatory standard for pH, which is classed as an indicator parameter, is a range of 6.5 to 9.5 at the customer's tap.

"A reading of pH 10 would exceed that standard."

It added: "An exceedance of an indicator parameter does not necessarily mean there is a risk to health but under Regulation 19 of the Water Supply (Water Quality) Regulations, if a water company has reason to believe a standard has been breached it has a duty to investigate the cause, as well as any other risks that may be associated with it."

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