A Waipawa water testing firm is urging farmers and lifestyle block owners to check their water regularly following an increase in the number of positive E. coli tests they have carried out.
Q Labs, formerly known as Quantum Laboratories, conducted 60 water tests from around the region over a period of 100 days, with 54 coming back positive for the bacteria.
CEO Raymond Burr said it was a case of "test, don't guess".
He said they had seen a significant increase in demand for testing for E. coli and other bacteria, mostly from farmers and lifestyle block owners who were relying on bores and rainwater tanks for their domestic water consumption, as well as for livestock.
"I think there is a general growing awareness amongst rural people that they have unprotected water supplies and that some of our water supplies out in the country areas aren't as good as people think they are."
Burr noted the increase in positive tests could also be down to the increase in the number of tests they were doing.
"More people are testing so of course the odds are that you are going to get a higher rate of E. coli positive."
He said contaminated water, particularly from water tanks, was a major cause of gastroenteritis.
"If you have one E. coli bacterium that makes it into that water tank and there's enough nutrients there, within 24 hours - if there are perfect growing conditions - you will have one trillion bacteria. So it happens really fast - it's exponential growth. Every 20 minutes the number of E. coli can double."
Testing for E. coli is recommended once a year if there are treatment protocols or a UV filter in place, otherwise it is recommended at three-monthly intervals.
If a water source supplies more than 20 people, testing needs to be carried out every three months under new regulations that came in 2016, but can be reduced to once a year after 12 months of clear tests.
A Hawke's Bay Regional Council spokeswoman said while it was not possible to comment on the results referred to by Q Labs, they "haven't noticed any increase in E. coli observations from our State of the Environment monitoring bores that would cause us to be alarmed about the state of the groundwater resource".
"E. coli is a faecal indicator that can come from many different sources. E. coli is not uncommon in shallow groundwater and surface water bodies, which may be from any number of sources in rural properties."
Similarly, a Hastings District Council spokeswoman said they "do not receive the test results from private supplies, but we encourage residents to undertake testing if they have any concerns about their water supply".
"If any property owner or resident wants assistance understanding the results our advice is to contact the District Health Board in the first instance."
Q Labs charges $28 for water testing, with results available in 24 hours.
If E. coli is detected, the Hawke's Bay District Health Board recommends boiling or chlorinating drinking water until the source of the contamination has been found and removed.
Contamination advice for owners of private bores and water tanks can also be found at healthed.govt.nz by searching for the word "water".