Your steamer is slowly turning hard water into rock. Here's how to stop it.

When water boils, the minerals in it don't leave with the steam. They stick to the inside of the generator, the heating elements and the sensors.

Scale causes a chain of trouble:

• Elements have to heat through a layer of rock, so they run hotter and burn out.
• Water level sensors get coated and read wrong.
• The steamer takes longer to steam, so food takes longer to cook.
• Valves and drains clog.

Much of the Midwest has hard water. A steamer here can scale up fast.

Most steamers have a descaling routine in the manual, often with a delime light or a cleaning mode. Use the descaler the maker calls for.

Set a schedule based on how hard your water is and how much you steam. Write the date down each time. Many kitchens let descaling slip during busy weeks, and that's when scale gets ahead.

If the steamer uses a water filter, change the cartridge on schedule. A filter slows scale. It doesn't stop it.

1. Turn the steamer off and let it cool.
2. Drain it, if your model calls for draining at close.
3. Pull out the pans and racks and wash them.
4. Wipe the inside of the cooking compartment.
5. Wipe the door gasket with warm, soapy water.
6. Leave the door open a crack overnight so the inside dries.

A door that doesn't seal lets steam pour out. That's wasted energy, a slower cook and a burn risk for whoever is standing in front of it.

Check the gasket for tears and hardening. Check that the latch pulls the door tight. Replace a worn gasket before it fails completely.

• Stand to the side and open the door slowly to let steam escape.
• Don't open a pressure steamer until the pressure has dropped, as the manual describes.
• Train new cooks on the steamer before they use it.

• It takes longer than normal to start steaming.
• Water leaks from the door, the drain or under the unit.
• A low-water, scale or error light comes on and won't clear.
• The steamer trips the breaker or shuts off mid-cook.
• Steam comes from places it shouldn't.