Most pressure canner brands (as of 2015) use rubber gaskets inside the lid cover to help seal in pressure:
A pressure canner is a deep, heavy kettle that has a rack on the bottom for jars to stand on, a tight-fitting lid with a gasket, and a pressure gauge. The gasket keeps steam from leaking out around the cover. If the casket is worn, stretched, or hardened, replace it.” [1] Fraser, Angela. Associate Professor/Food Safety Education Specialist. How Canning Preserves Food. Clemson University, Clemson, SC. Accessed March 2015 at http://www.foodsafetysite.com/consumers/resources/canning.html
The pressure canner brands that use a gasket include Presto, Mirro (and the now-discontinued Fagor.)
Only one brand (as of 2020) does not, which is All-American: “It has a metal to metal seal, so there is no need to replace rubber gaskets.” [2] Utah State University Cooperative Extension. General information about pressure canners. https://extension.usu.edu/utah/files/uploads/Master%20Food%20Preservers/PressureCanners.pdf. Accessed 2015. [A vintage brand, Kook Kwik, also used no gasket.]
NCHFP recommends changing rubber gaskets and rubber overpressure plugs just as a routine matter of course every 2 years [3] Andress, Elizabeth L. Pressure Canning and Canning Low Acid Foods at Home. Cooperative Extension: University of Georgia. Powerpoint presentation, slide 36. Accessed March 2015. .
Some people say they replace their gaskets every five years (but don’t say how often they use the canner). Others say they wouldn’t push it that long: “As to a gasket lasting 6 years one of these days you will have a gasket blowout. They get brittle over time and are less stretchy. That’s when they blow.” [4] User comment at https://www.canadianpreppersnetwork.com. March 2013. People say you’ll never know just how high you can jump until you’ve had an old, weak pressure canner gasket blow on you in mid-operation.
Some end users say they always keep a spare replacement set handy. The question usually eventually arises of how long a “spare gasket” in storage is good for. The University of Maine Extension seems to say five years: “Gaskets in unused lids work well for at least five years from their date of manufacture if stored in a cool, dry area.” [5] Let’s Preserve: Steps to Success in Home Canning. University of Maine Cooperative Extension. #4079. 2007. Page 3.
Presto, however, says you cannot store spare gaskets at all: “We do not recommend storing them, rather buy fresh each time you need to replace the rings. The rubber can and will deteriorate over time. ” [6] Shelly at Presto Customer Service to healthycanning.com. 4/17/2015. Correspondence on file. This could make having a gasket fail on you right at the start of a canning session quite problematic.
References
Shirley
Our pressure canner never built pressure but we left it on the heat for three hours and the chicken we had in there looks cooked and the jars are sealed do you think it’s safe?
Dan
I do not see any way to order replacement rubber gaskets for the 22 quart pressure canner, model 92022. Lots of information, no way to order parts. That’s a pity.
Healthy Canning
You need to contact the maker of your pressure canner for that kind of hyper-specific canner part information.
Douglas
Huh. I’ve been using my gasket for over 7 years. I guess it doesn’t know it should have failed by now!
Patricia Ruddy
Can I use a mirro canning gasket in place of a presto gasket
Healthy Canning
Sorry, no idea. Ask Mirro.
Jeanne mclaughlin
Can i replace my rubber gasket lid for a metal to metal lid
Healthy Canning
Probably not, but you’d need to check with the manufacturer of your canner.
Dan Hartman
No, the “only”(?) canner company that does not need a gasket to form an airtight seal is the All-American canner made in Wisconsin. They are designed and manufactured so that the canner pot mates up with the lid and forms a perfect seal. The other canners are not machined in the same way which is why an All-American canner lid will not fit a Mirro or Presto. (Not to mention that they latch in a completely different way.)