It wreaked havoc across parts of Lancashire for more than a month, and cost water bosses millions in compensation.
Exactly one year ago today, families and businesses throughout the county were warned to boil all drinking water after a microscopic bug posing a health risk was found in tap supplies.
But, 12 months after traces of cryptosporidium were first discovered, scientists are STILL unable to reveal how it got there.
An investigation was launched by the Drinking Water Inspectorate (DWI) into the contamination, but has still not reached a conclusion on what caused the major health scare.
Here’s how we reported the crisis one year ago:
It carried on for a long time, people were getting really cheesed off.
A DWI spokesman said: “Investigations are ongoing and we will be putting information into the public domain as soon as we are able to.
“It’s a large and complex system and there are a number of lines of inquiry which need to be pursued to their conclusions.”
Bosses at Public Health England said they were also waiting for a report from the DWI, while water firm United Utilities added: “We are still co-operating with the Drinking Water Inspectorate’s ongoing investigation. The findings will be made public once the investigation is complete. The timing is a matter for DWI.”
It was exactly one year ago - on August 6, 2015 - when more than 300,000 homes and businesses were first warned to boil all drinking water to protect against the nasty parasite.
Preston, South Ribble, Chorley and the Fylde Coast were affected and it took 30 days for all supplies to return to normal, leading to compensation payments of between £50 and £60 to all domestic consumers and much more to businesses affected by the alert.
A dead pheasant in an outflow pipe was the most popular theory as to the source.
When the investigation was launched, it centred on the United Utilities water treatment plant at Franklaw near Garstang.
The warning not to drink tap water without boiling it first caused disruption across the county, with some families and organisations struggling to access bottled water.
Melanie Close, chief executive of Preston-based charity Disability Equality North West, said: “It was all right if you were fit, healthy and could jump in your car and buy water, but if you weren’t, you were struggling.
“For us as an organisation, we had to be really really careful because we’ve got staff and volunteers - it’s an extra job for us telling people they can’t have the water or cordial.
“Then you get the compensation which is next to nothing.
“And they are still not telling us why it was caused, and they didn’t at the time.
“And the vaguer they are, the worse it is for somebody with a long-term health condition, because some people who were fit and healthy were just saying ‘we are still going to use it.’”
Peter Titterington, who has mobility problems and uses a wheelchair, said the warning that water must be boiled caused problems for him at the time.
Peter, 63, who lives in Deepdale, Preston, said: “Because I live in sheltered accommodation, some people did have problems getting water delivered.
“Luckily my daughter ended up buying bottles and bottles of water - I think she bought the shop out - it was very kind of her.
“A few people complained because they had to boil their water and let it cool and they couldn’t be bothered, and they were all asking what caused it.”
Peter said his daughter, Mary, was able to fill her car boot with bottles of water and deliver it to the sheltered housing, but said: “I think I would have struggled otherwise.
“I think maybe eventually somebody would have got some, but it heavy carrying it.
“I can’t carry stuff, my arms are weak as well so I can’t really carry pans or anything, and I need help to even fill my kettle sometimes.
“So, personally, I did have problems.
“Luckily my girlfriend who lives in the same building helped me out, she went to the shop for me, but she has problems walking as well.
“It carried on for a long time, people were getting really cheesed off.”