Michigan’s water crisis forced Colorado to change its tests for lead contamination

Water providers across Colorado, including Denver Water, are changing the way they test for lead and copper in the wake of the Flint, Michigan, health crisis.
5 min. read

Water providers across Colorado, including Denver Water, are changing the way they test for lead and copper in the wake of the Flint, Michigan, health crisis.

The revision comes about two months after employees of Flint and the state of Michigan were hit with numerous charges for allegedly manipulating the results of water tests.

Among the accusations: that Flint biased test results by encouraging residents to "pre-flush" their lines by running their taps for five minutes before tests. And until very recently, the state of Colorado was one of many governments that suggested water testers do that very thing.

What changed?

Prior to now, this is the method that Colorado Department of Public Health and Environment recommended for testing home taps for lead contamination:

  • The resident runs the tap on cold "for several minutes," a.k.a. pre-flushing
  • The tap is turned off and left alone for at least six hours
  • A tester fills a glass with cold water, then tests it for contaminants

All the state's various utilities require the six-hour stagnation period, but they have had different interpretations of the initial pre-flush step.

Denver Water, for example, has recommended that residents simply run the tap until it is cold, prior to the stagnation period. A Denver Water spokesman says this is not the same as pre-flushing, as it normally should take only a few moments. (However, the utility did recently tell about 100 customers that the process could take "a few minutes.")

Either way, the federal and state governments now have recommended the elimination of anything resembling a pre-flush, and Denver Water will follow suit in its next round of testing.

Why was the old policy in place?

First, let's review two facts about lead contamination:

  • The longer that water sits in a pipe that contains lead, the more lead it may extract from that pipe.
  • Hot water extracts contaminants faster than cold water.

So, if water sits in a lead-containing pipe for a couple weeks before a test, that water sample would test higher than a sample that sat for only a few hours.

This introduces variability, potentially causing different results for otherwise identical scenarios. The state's old policy – run the water, then leave it sitting for six to 18 hours – aimed to make the tests more uniform and eliminate false positives.

CDPHE previously described the pre-flush as a way "... to flush out any 'old' water ..." before a test, according to a document provided by the department.

Denver Water, meanwhile, previously aimed to "... remove variability that could be associated with occurrences such as extremely long stagnation periods or use of hot water prior to the stagnation period," wrote Travis Thompson, a spokesman for the utility, in an email to Denverite.

What's the harm?

The longer the flush, the more lead that it temporarily removes from the line, according to a paper published by Marc Edwards, the Virginia Tech professor who helped bring Flint to national attention.

The argument against pre-flushing, then, is that it could drive test results artificially low, failing to capture the "worst case" scenario and, according to Edwards, violating the intent of federal law. The Guardian reports that the federal Environmental Protection Agency has warned against pre-flushing since 2008.

How common was this practice?

An investigation published last week by The Guardian identified 22 U.S. cities that encouraged pre-test flushing, describing it as one of several "cheats."

The city of Flint had people flush their lines for five minutes. Testers in Washington D.C. reportedly flushed lines in schools for more than 45 minutes in the 2000s. Philadelphia has encouraged a two-minute cold-water flush, The Guardian reported.

The Guardian's report also described two other tactics that could drive results down: Some have testers remove aerator caps or run water unusually slowly during tests. Denver Water says it hasn't employed those strategies, and the state didn't recommend them.

In February, the federal Environmental Protection Agency issued a "clarification" that recommended against pre-flushing and other practices. Colorado officially recommended its change in policy with an email last month.

Should I be worried?

Denver Water, which serves the city and its suburbs, says its water sources and delivery lines are free of lead, but the contaminant still can creep in through buildings' plumbing – which is part of the reason that the utility tests tens of thousands of water samples annually for contaminants.

The threat of lead is highest in homes built before the mid 1950s and in 1980s homes with copper piping, which often used lead solder. Denver Water and other utilities offer free water tests for the contaminant, which can cause neurological impairments.

Thompson, the Denver Water spokesman, says that tests conducted under the old protocol remain valid, especially because the utility advised a relatively short flush.

"The update language isn’t much different from what we’ve asked testers to do in the past, therefore we don’t anticipate much, if any, change to future results based on the revision," Thompson wrote.

But Edwards, the professor, suggested in an email that he "would re-test, using procedures that did not hide water lead problems."

As for the longer flushes recommended by the state: We're awaiting comment from CDPHE as to whether retests will be necessary.

Thompson adds that "no level of lead in water is safe." If you're worried about lead in your home, request a test from Denver Water or your respective utility.

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