Beware those who bring bad tidings about your water. On Tuesday, the Minnesota Department of Health issued a public warning about deceptive sales of water treatment systems.

In the worst cases, the sales pitches have featured faked water tests, bogus claims of contamination and "grossly inflated prices" for treatment that's often unnecessary, the Health Department said. Dishonest salespeople have apparently capitalized on unease about widespread groundwater contamination by former 3M industrial chemicals in Washington County, the department noted.

The Health Department recommends you check out the company's background, not to mention its claims about your water, before signing up. The agency maintains a font of information about wells and water treatment. Complaints about unethical practices should be made to the state attorney general at 651-296-3353 or at this site.

Have the water scaremongers come to your door?