A damaged air valve on a pipe in a field containing cattle has been identified as a potential source leading to the existence of small traces of parasite in a local water network.

Around 16,000 households and businesses in the Brixham area of Devon have been told not to use their tap water for drinking without boiling and cooling it first.

South West Water’s (SWW) chief customer officer, Laura Flowerdew, said it is possible that cattle manure caused the contamination.

The UK Health Security Agency (UKHSA) said 22 cases of cryptosporidium, a waterborne disease caused by a microscopic parasite, had been confirmed in the fishing town.

Other reported cases of diarrhoea and vomiting in residents and visitors are also under investigation and more confirmed cases of cryptosporidium are expected, the UKHSA said.

SWW issued a “boil water notice” for Alston and the Hillhead area of Brixham after water tests showed “small traces” of the parasite cryptosporidium, which causes sickness and diarrhoea.

Ms Flowerdew told Sky News: “We have identified that there is a damaged air valve on our network just near the Hillhead reservoir but we absolutely want to make sure that that is the only source and therefore are just ensuring that we’ve gone through all the right operational procedures.”

Asked if it was animal faeces that infiltrated the network, she told the broadcaster: “We understand that this is a valve on one of the pipes that head towards the Hillhead reservoir, not on the reservoir itself.

“It’s in a farmer’s field and I understand that there are cattle in that field and therefore there’s a possibility that that is therefore the source of the contamination.”

She added that work is still under way to determine the cause of the contamination but that the damaged air valve “does look like it’s a potential source”.

Ms Flowerdew would not say how long the issues will last, telling Sky News: “We are working hard to be able to give more decisive information about that timeline.”

SWW initially said it would pay £15 in compensation to customers but this has been increased to £115.

The company’s chief executive, Susan Davy, said they have been delivering bottled water to vulnerable customers and local business, including schools, and made it available to residents.

Eden Park Primary School was closed on Thursday due to not having drinking water.

Ms Davy apologised for the incident: “To those in the affected area and our customers across the South West, I am truly sorry for the disruption and wider anxiety this has caused.

“While incidents like these are thankfully very rare, our customers expect a safe, clean, and reliable source of drinking water.

“I know on this occasion we have fallen significantly short of what you expect of us.”

Anthony Mangnall, Conservative MP for Totnes and South Devon, attended a meeting with the Department for Environment, Food and Rural Affairs to receive an update from South West Water (SWW) and the UKHSA on Thursday and said residents are likely to have to boil water for another week.

Mr Mangnall added: “I am very concerned about SWW’s response to this situation, as they have been slow to act and communication with customers has been very poor.

“This has certainly undermined trust in our water network and I will certainly keep working with colleagues at Defra to ensure SWW are held to account over this issue.”

The company previously said data from tests on Tuesday had shown treated water leaving its treatment works was not contaminated, but further tests taken overnight found small traces of cryptosporidium and it had issued the warning to boil water as a precaution.

Residents are being urged to boil water and let it cool before drinking it, preparing or cooking food or cleaning their teeth, though the company said water can continue to be used as normal for washing, bathing and flushing the toilet.

The disease can be picked up directly from the faeces of another person or animal, from swimming in or drinking contaminated water, or even by eating contaminated food such as unwashed vegetables.

A No 10 spokeswoman said: “The Prime Minister understands the stress and worry this has caused residents.

“He’s very clear that this must be investigated thoroughly by the Drinking Water Inspectorate and UK Health Security Agency.”

The Government has announced a quadrupling of inspections and provided increased powers to Ofwat and the Environment Agency to hold water companies to account, she added.