Seventy-one percent of the Earth’s surface is covered by it and humans could not survive without it, but surprisingly little is known about what’s in water flowing from taps across the U.S.

If there’s one difficult lesson the nation learned from the Flint water crisis, it’s that ignorance is not bliss.

This week, while politicians and bureaucrats continue their decline into a blaze of finger pointing, the Associated Press released stacks of government testing data collected since 2013 from both public and private water systems nationwide that shows elevated lead levels were detected in more than 1,400 locales.

The quest for “who knew what and when?” in Flint triggered many to ask, “What do we know about our own water?”

The answer: not enough.

Most of those systems highlighted in the data likely pump clear, fresh-looking water that wouldn’t evoke a community outcry like the yellow-tinged, odorous flow that triggered concern from residents in Flint.

Testing results are dispersed according to state and federal regulations to people whose water originates in those systems. The samples are collected at both distribution facilities and at a fraction of taps served by such systems.

But it’s what doesn’t appear in those data tables that highlights both the need for more uniform and comprehensive testing requirements and a significant dose of personal responsibility on the part of homeowners to protect their families.

The reports outline how there is no requirement that schools and child care centers – places packed with those most vulnerable to the effects of lead poisoning – conduct regular water tests.

And the hundreds of thousands of homeowners who draw their water from wells shoulder all responsibility for knowing what’s in their water.

Moreover, results published from places where regular test data is available can provide false security.

The AP reports that operators of community water systems are required to test water once each year – more often if elevated lead levels are detected – and they are considered out of compliance if more than 10 percent of samples return showing contamination.

Those same rules require operators test samples from as few as five taps, depending on the size of the system.

It’s a game of statistical roulette playing out nationwide.

Experts are quick to point out that lead levels can vary wildly from tap to tap within a single water system because of variations in plumbing and infrastructure from street to street, house to house and even within a single home.

That variability creates a near impossible task for water system operators whose job is to provide clean drinking water to customers.

Test results posted by Traverse City’s public works department from 2014 show no samples taken that year exceeded standards. But results from tests conducted three years earlier show two samples exceeded “acceptable levels.”

Information published with the city’s test results states the city “cannot control the variety of materials used in plumbing components.”

Operators could declare water safe based on sampling results, yet one home or even a single tap within a system – because of lead contained in plumbing fixtures – could flow contaminated water while others do not.

Therein lies the problem facing water utility officials and homeowners alike – a sample is only as good as the tap from which it flows.

– The Traverse City Record-Eagle