Commerical coffee machines have been described as Club Med for cockroaches - with one technician finding the insects in about 10 per cent of the equipment he services.
David Hollick, who has 20 years' experience, said some machines contained a few, but others were infested.
"You take the sides of the machine off and they scatter," said Hollick, who works for Atomic Coffee Roasters.
"Cockroaches love coffee machines - it's like Club Med for them."
Mike Gerbic of Espresso Engineers said he had seen things to make any coffee lover choke on their latte during 12 years in the industry.
"A lot of machines are in quite a state - everything from your typical coffee and hot chocolate build-up to cockroaches running amok everywhere.
"I'm sure if the health department knew what was inside the machines they'd probably close the cafes down."
Auckland City Council environmental health team leader Carol Simpson said her organisation's regular inspections of food premises included equipment checks and asking staff how they clean their equipment.
The insides of coffee machines were not inspected, but Simpson was adamant cockroaches would be noticed because they would be elsewhere on the premises.
"If there's a cockroach infestation they wouldn't just be inside the machine. That's something we'd definitely pick up on.
Cockroaches aren't the only problem.
Both Gerbic and Hollick have come across rat and mice droppings and said rodents can gnaw through the wiring. Restaurant Association of New Zealand president Mike Egan was "surprised and disappointed" machines in some establishments were poorly looked after and thought councils should be cracking down on those responsible.
"If cafes and restaurants have cockroach infestations, that's the operator's fault, but maybe local authorities should be doing more."
Egan said many eateries had the "odd cockroach, but if there's an ongoing problem, that's terrible".
Simpson said that when cockroach infestations were found, the offending establishment was usually closed down and a pest control company called in.
If things improved, the eatery was reopened with an E grade.
She urged technicians and other members of the public to contact the council if they noticed cockroaches.
Experts said machines should be cleaned thoroughly and serviced at least every six months, a process that generally costs several hundred dollars.
"The cafes that are doing well are the ones that look after everything in their cafes, including their machines," said Gerbic.
Derek Townsend of Karajoz Coffee Company said it was a "constant battle" to ensure his clients were as passionate about machine cleanliness as him.
"We try to get through to the customers that it's well worth keeping your machine in good condition and cleaning it properly. It makes such a difference to the quality of your coffee and therefore you sell more coffee and do more business."By Alice Neville