Boil water advisories have dramatically improved over the past decade.

In May, 2000, E. coli O157:H7 entered the improperly chlorinated water supply of Walkerton, Ont. (that’s in Canada), sickening about half of the town’s 5,000 residents and killing seven.

Soon after a boil water advisory was issued, residents had questions, like what about brushing teeth with contaminated water, or showering? The advice was confusing.

Christchurch, New Zealand has been under a boil water advisory since the Feb. 22, 2011 earthquake. Yesterday, the Ministry of Agriculture and Forestry (MAF) reminded food businesses in Christchurch that the city-wide boil water notice also applies to coffee machines.

Coffee machines?

MAF director of compliance Geoff Allen says some businesses have been surprised to learn that the boil water notice relates to espresso machines, which are plumbed into the city water supply.

“Most of these coffee machines only heat water to 80–85°C, which is not sufficiently hot to kill off illness-causing bugs like giardia and cryptosporidium, so these machines need to be turned off or hooked up to a supply of pre-boiled water.”

He suggests that if you want to know whether your latte or long black is safe to drink, ask where the water came from. “If in doubt ask for a cup of instant or plunger coffee, where you can adequately boil the water beforehand.”

Bringing water to the boil is sufficient to kill off any bugs that are present.

A range of other machines which are plumbed into the city water supply are also affected by the boil water notice, including slush-ice makers, ice machines, postmix guns, self-service soft drink machines and some water coolers. “These machines should not be used until the boil water notice has been lifted or the water they are using has been boiled.”