MILWAUKEE - The City of Milwaukee has been named as one of the 33 cities across 17 US states have used water testing "cheats" that potentially conceal dangerous levels of lead, according to a newspaper investigation.



The Guardian, a British newspaper with a U.S. edition, launched an investigation in the wake of the toxic water crisis in Flint, Michigan, and contacted 81 U.S. cities the methods they used to test drinking water for lead.



The Guardian found that lead testers in Milwaukee were instructed to 'pre-flush' water pipes before testing for lead content, which is against EPA rules. The Guardian called 'pre-flushing' pipes a way to improperly manipulate the collection of water samples that could "temporarily hide" lead contamination.



Milwaukee was not alone in 'pre-flushing,' as the Guardian found 20 other major cities engaging in the practice.



Other findings:



Testers removed aerators from spouts before running water in 7 cities, which can reduce lead content



In 23 cities, testers were told to run water slowly, which causes less lead to be dislodged from pipes.



The Guardian also said that Philadelphia, a city accused of having the worst water testing in the US, asks testers to pre-flush their pipes, remove aerators and slowly pour water into a sample bottle. The EPA has warned against all these testing methods, which could "mask the added contribution of lead at the tap".