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Sterilizing Water in a Pressure Cooker

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This method Sterilizing Water in a Pressure Cooker is much like pressure canning. Except instead of sterilizing food, we will be sterilizing drinking water in glass canning jars. Unlike filtering or distillation, this will not do anything for contaminate – just organisms.

To truly sterilize something, it must be free of all microbes AND spores.

Boiling does NOT kill all bacteria. Some bacteria are actually resistant to the temperature of boiling water at 212° F. (100 ° C.). Many bacteria formed spores can withstand boiling.

To kill all the bacteria, you need to raise the temperature to about 250° F. (121° C.). Sterilizing with steam heat is the most common method to obtain this level of sterility.

It is also the most effective, since spores can resist dry heat, but 30 minutes of exposure to steam at 250° F. 121°C will kill almost anything.

As a matter of fact, pressure canners kill so effectively, you can use them to sterilize medical equipment.


  • Add approximately 2 inches of water into the pot.
  • Place the supporting rack inside.
  • Fill the canning jars with water, leaving 1 inch head space before closing the lid, and only tightening the bands just finger tight.
  • Add the water filled jars to the pot.

For Canners or Cookers with A Weighted Pressure Regulator

  • Lock the lid in place, but do NOT place the weight on the vent pipe.
  • Turn the heat to high
  • As soon the water at the bottom of the pot begins boiling the steam will displace the air inside the unit.
  • Let the steam escape from the cooker or canner in order to expel the air.
  • Wait until a good jet of steam is venting from the vent pipe before replacing the pressure regulator weight on the vent pipe.
  • Once the pressure setting reaches 15psi, turn down the heat and start a 30 minute timer.
  • Make sure the pressure setting remains constant, if pressure drops, get back up to 15 psi and restart timer.
  • After 30 minutes, turn off the heat and allow the pot to cool naturally until the pressure slowly drops.
  • The jars of sterile water should now be removed immediately.

As long as the sterilized liquid remains sealed the jars should be free of microbes until it is opened again.

It occurs to me that if you are having to sterilize water in a pressure cooker, the chances are good you kitchen stove isn’t working so I have included below instructions in using a pressure cooker on a wood fire.

If your pressure cooker is stainless steel and does not have any sort applied coating or non-stick finish, it can be heated outside over a wood or charcoal fire.

  • Start by digging a shallow depression in the dirt and build a fire in it.
  • Build up a large enough fire to produce a deep bed of coals.
  • Position the canner in the heart of the coals.
  • Cooking on a fire is harder than on a stove because it will be necessary to reposition it in order to maintain proper pressure
    Moving it in or out of the hottest part of the coals as needed.

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