Washing machines have come a long way since the first electric model went on sale in 1907. That machine, dubbed “Thor” by the Hurley Electric Laundry Equipment Company, wasn’t exactly waterproof, which made for rather dangerous operation when plugged into a wall. More than a century later, these appliances automatically conserve water, dispense detergent at optimal times, and even wash delicate cycles in a separate drawer. Unfortunately, the durable machines can also be put out of commission with something as simple as a quarter.

As Reader’s Digest recently pointed out, consumers loading their washers often make mistakes that can result in substantial repair bills. The worst one? Not emptying pockets to remove loose change. James Peters, Kenmore's laundry product manager, told Reader's Digest that these tiny projectiles can harm washers in a number of ways. They can damage the drain pump or get stuck there, causing problems with water drainage; during high-speed spin cycles, they could also shatter the glass of a front-loading door. Peters advises to check pockets thoroughly before tossing anything inside.

Another washing hazard? Lingerie. The hooks and straps found in more delicate attire can latch on to other clothes, ripping the material or even damaging the drum of the machine.

You’ll also want to double-check that none of your clothes are hiding your car keys: The electronics in a key fob could be ruined when submerged in water, and the keys can easily scratch the interior. Running shoes are also questionable, as shrinkage can lead to a poor fit.

Tiny clothing like baby socks should be put into a mesh bag, so they don’t have an opportunity to get stuck in one of the machine's vents or hoses. Waterproof jackets are also a bad idea; it might seem contrary, but these items can trap water and explode during spin cycles, creating balancing issues and other damage.

Today's machines might seem like mechanical beasts, but a couple of pennies and a pair of baby mittens can be their undoing. Taking these precautions could save you a lot of grief—and a lot of money.

[h/t Reader’s Digest]