A number of outbreaks and pseudo-outbreaks have been associated with contaminated rinse water in endoscope washer-disinfectors. Health Technical Memorandum 2030 specifies that final rinse water should be ‘bacteria-free’. In this study, results of rinse-water testing from 20 endoscopy units were reviewed over a 4-month period. Over 60% of samples were of an unsatisfactory quality (i.e. not bacteria-free) and none of the endoscopy units consistently achieved sterile water throughout the study period. Poor microbiology results caused anxiety to endoscopy staff and infection control teams who had to decide whether or not to take washer-disinfectors out of use, possibly resulting in delays to medical procedures. There was no common policy on how to react to poor results, with staff at each unit developing their own action levels. Here, it is suggested that future guidelines would be of more practical use if they specified a series of action levels of increasing severity based on the bacterial count in a water sample.