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Overdosing can be a real problem for many Americans. We're talking about people using too much laundry detergent, an issue perhaps caused by user mistakes or by poor design of the caps on some containers and bottles—or maybe a combination of the two.

During the testing for our latest report on laundry detergents (available to subscribers), technicians and other staffers noted how hard it was to decipher the fill lines on several caps.

"If the lines aren't clear or are hard to see, it's easy to overdose and use too much detergent," says Pat Slaven, a program leader in our Technical department who conducted the detergent testing. "Plus, for all the products we tested, the line for a medium load—the most commonly done load—is less than a full cap, which makes it easier to use too much detergent." The line for a maximum load is also typically less than a full cap.

Since some of the tested detergents cost as much as 65 cents per load, using too much cleaner could become expensive. Overdosing can also cause soap deposits and lint to form inside your washing machine, which, say some manufacturers, might contribute to mold and odors. It could also plug or restrict ports or filters, says Chris Zeisler, an appliance-repair expert at RepairClinic.com, who adds that those deposits could result in mechanical failure. And for some high-efficiency washers, overdosing can produce excessive suds and lead to extended wash cycles as the machine tries to remove the soap.

"I've been in a lot of focus groups with consumers who say they're ruined high-efficiency machines because they used too much detergent," says Michele Hall, Pod director at Method Products, a maker of detergents. "With the growth in high-efficiency washing machines that are so sensitive to overdosing, it's important that people learn how to dose properly."

Even a textiles expert can face issues with detergent caps. "The salesman who sold us our energy-efficient washer emphasized that we should follow directions to the letter—or fill line, in this case. Of course, I have to stand under a floodlight in the garage to see the fill line," says Margaret Rucker, Ph.D., a professor of textiles and clothing at the University of California at Davis. "If a study on cap design hasn't been done, then it should be," she adds.

Some manufacturers have tried to address overdosing. "The way we thought about cap design was to expose the dirty little secrets of the [laundry-detergent] category, and one of them is overdosing," says Hall. "It's consumers' natural behavior to overdose. People want to add in a little more for cleaner clothes, or they're used to dosing at a certain level, or the lines are pretty hard to read so that consumers either don't look for them or aren't able to read them."

Another manufacturer has taken a different approach to solving the problem. "We feel the best practice is to include a picture of the cap on the directions, where we call out exactly where the dosage lines are on the cap," says Bill Littlefield, executive vice president and general manager of branded products of the Sun Products Corporation, which makes All and Wisk detergents. Littlefield admits, "It's a struggle to find proper dosage."

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