When I get a new pressure cooker, I pressure-cook water in it. I do this with every pressure cooker — even if it's the same model, size, or brand. That's because this "hot water test" not only reveals how the pressure cooker works and how much water does not evaporate, but it can also spot any issues or defects with the cooker.
Why This Test Is Important
Pressure-cooking water is invaluable for those who are new to pressure cooking; it takes away the mystique and misconceptions of pressure cooking. I've seen beginners give up after five minutes thinking that their electric pressure cooker was broken because it didn't start cooking. Before pressure cooking can begin (i.e., the timer starts counting down), the water inside has to come to a boil, the steam has to push out the air, the valve has to close, and pressure has to build. This whole process can take anywhere from 10 to 15 minutes. Knowing what to expect and how long it will take removes the guesswork and fretting from pressure-cooking your first meal.
The Evaporation Difference
The hot water test gives the cook a peek into how little liquid evaporates during pressure-cooking. I boiled the same amount of water in an uncovered pot and in a pressure cooker for 10 minutes to see the difference. The uncovered pot evaporated approximately a cup of water, while the pressure cooker only lost about a tablespoon. Seeing the decreased evaporation highlights one of the big differences between pressure and conventional cooking. All that "extra" remaining liquid can make for a very watered-down tasteless hunk of meat.
Troubleshooting Your Pressure Cooker
If something didn't turn out as it should, it could be an equipment problem or it could be the fault of the recipe. Were you able to pressure-cook water without problems? Did the problem persist during the hot water test, too? Then it's an equipment problem; gaskets and valves need to be replaced regularly (every 18 months or so). When these parts start to wear, the cooker will have difficulty reaching and maintaining pressure. For something more serious, like the pressure cooker doesn't turn on, it's time to call the retailer or manufacturer for a replacement.