How to install the Seal on a Presto 21-B Pressure Canner

Having trouble with that flat seal on your vintage canner?

Presto 21-B pressure canner seal installation with video.

The flat seals on the National Number 7 canner clones, such as the Presto 21-B are sometimes a royal pain to insert properly. They fit into a groove in the canner lids and if you are not careful, they will not get seated properly. Sometimes they can stretch and be even more difficult to fit.

After you’ve done it a few times, it doesn’t seem to be so bad, but the first time – you almost always think you have the wrong seal!

You push the seal into the groove from the inside out, working in small sections, constantly making sure that the seal doesn’t pop back out as you move on. Sometimes you have to start over. Sometimes you have to work your way around the lid a couple times. And, sometimes, the seal is just too old and stretched to fit any longer. When that happens you need to order a new seal.

The Presto part number is 09907.

Here is a brief video showing how I do it.

Amazon Image
Amazon Image

Pressure Canner Refurbishment

Suggestions on fixing up an old canner.

Refurbishing and upgrading your old pressure canner.

If you have an old canner in a closet or found one at a yardsale, the following articles may help you get it working again. Please check with your local extension agency office for gauge testing, if your canner has a gauge.

Safe Canning Tips

Just because grandmaw did it that way doesn’t mean it’s the correct way to do it now.

Now don’t get me wrong here, I ain’t dissin’ your grandmaw. I’m sure your granny was a wonderful lady. Mine sure was. But, just because she did something a certain way, doesn’t necessarily mean you should. We have access to technology, testing, and good old science that our grannies didn’t.

  • Hey! My grandmaw did it THIS way and she never killed anyone.
    That you know about. While we can’t go back in time and prove it there has been speculation that mysterious deaths in the past could have been caused by canned foods that were not safe. We have many more years of knowledge that she didn’t have available to her. How about let’s go with the scientists here?
  • You can boil green beans for 3 hours and they’ll be safe.
    No. Actually you can’t be sure of that. You might get lucky. You might poison someone. Research tells us that it would take more than 12 hours in a boiling water bath to ensure their safety. For the record: I’m not eating green beans you BWBathed. And I’m not letting my family eat them. And I’m going to discourage your family from eating them.
  • Dry canning is safe.
    What do you mean by “dry canning”? If you mean putting dry foods in jars, putting lids on those jars and putting it all in the oven – um, probably not a great idea. Canning jars aren’t supposed to go in an oven. The glass isn’t meant for that dry heat – it can shatter! The newest recommendations for lids is to not even simmer them, much less throw them in a hot oven! If, by “dry canning”, you mean vacuum sealing with something like a FoodSaver – yeah you can do that.
  • You should turn your jars upside down after processing to make sure they seal.
    No. Not really. Even where this is written down as an approved method, it is said to be questionable. You are dealing with the safety of your family here, not to mention yourself, do you really want to take a chance? We know that turning jars upside down can allow food to get between the rim of the jar and the lid and cause a seal failure.
  • My granny left the rings on her jars, why should I take mine off? Just because you say so?
    Not just because I say so. How about three reasons? One, and most important, is that the ring can hide from you an unsealed jar and you may not know it’s spoiled – the ring can hold that lid down. Two, hygiene, pure and simple – there is frequently foodstuffs under those rings and: eww. Three is money. If you remove your rings you can wash them and reuse them for your next round of canning.
  • I’ve got a big family and I’m going to can my green beans in half-gallon jars. It’s ok because I’m using a pressure canner, right?
    Just because you are using a pressure canner, does that mean that the heat has reached all the way to the middle of those big jars and has been hot enough long enough to kill everything that could kill you? You can’t be sure. Only high-acid juices are approved for canning in half-gallon jars.
  • About that heat reaching the middle of the jars thing . . . is this why pumpkin puree is not safe? I don’t need a half-gallon of that!
    Pumpkin puree is very dense though, isn’t it? I mean when we dump it out of a commercial can, it pretty much sits there without slumping, doesn’t it? It’s so thick and dense that the heat can’t get through to all areas of the jar – leaving some areas under processed and unsafe.
  • I’ve got this great recipe that’s been handed down in the family. I’m going to can that!
    Has it been tested so that you know how long to can it to make it safe? I didn’t think so. Maybe you should reconsider and use only tested recipes.
  • I’m going to do it the time-honoured, traditional way!
    You can also speed and maybe you don’t get a ticket. I don’t recommend it; eventually the Officer Botulism will catch you.

I recommend going to the website of the National Center for Home Food Preservation. They are the ones who do the testing, after all.

Electric Canning Burner Elements

Do your canners take too long to come up to temperature on your electric coil stove? Maybe it’s time for a burner element upgrade!

If you’ve been spending a lot of time canning on your electric coil stove, you may have noticed a few things about your elements and stove-top and how they perform together:

  • Maybe your stove-top is hotter than you think it should be while you are canning
  • Maybe the coils of your burner elements are sagging or warped or twisted
  • Maybe your stove-top is sagging under the weight of loaded canners
  • Maybe your canners seem to be taking forever to reach temperature

The sagging stove-top

I’ll tell you right off the bat that not every stove is designed with large canners in mind – or large pots of any kind. So many of us do not cook at all, much less in the quantities that would require a 22 quart stock pot or a 30 quart canner. Manufacturers won’t design their stoves for a big ole water bath canner if they think we will only use the stove to heat 6 ounces of water for a cup of tea. If your stove-top is sagging under the weight, this article isn’t going to be much help to you, I’m afraid. You’ll need to consider other alternatives. A new stove. Or canning outside on a camp stove.

Since many stoves aren’t designed for big pots, it follows that neither would be the elements. A manufacturer will frequently put in elements with lower wattages and with brackets only strong enough for that afore-mentioned cup of tea. Those elements are certainly powerful enough and strong enough for “normal sized” cookware, but when you want to bring a large quantity of water to boiling, and keep the element from collapsing, you frequently run into trouble.

The stove-top is too hot

If you’ve noticed your stove-top being much hotter while canning than during your normal cooking, take a look at the height of your existing coil elements. You’ll notice that they are probably no more than 1/2 inch above the surface of your stove-top. A canner or large stock-pot will over-hang your big burner, usually by at least 2 inches all the way around. This will trap heat between the bottom of the canner and the stove-top. That excess heat could damage your stove-top, the drip pan under your burner or even the receptacle that your burner plugs in to.

Burner elements that are designed for canning are usually higher than the standard burner that ships with most typical stoves. The True Canning Burner listed below is right at 3/4 inch above the stove-top, while the Jenn-Air Big Pot is closer to a full inch. This extra space allows for much more air flow under the canner and keeps your stove-top noticeably cooler.

If your receptacles are damaged, you will not get full performance out of your elements. When you remove your elements for cleaning, if you notice any burnt places on the prongs that plug in to the receptacle, you definitely need to replace your receptacles and almost certainly need to replace your element.

The coils are sagging

Canners and large stock-pots are much heavier than your “normal sized” cookware, even when they are empty. If you fill a typical 22 quart stock pot with water you will easily approach 50 lbs, and all of that weight is resting directly on your burner element. When the coils get hot and are underneath all that weight, they will sometimes warp or sag or otherwise stretch out of shape.

A typical element will have a tripod type bracket under it. Simply three legs in a Y shape to hold up the coils and support the cookware. Burners designed for canning will usually always have a heavier-duty bracket under them and one that is designed with more support for the coils.

Probably the most common – and it’s possible you already have these – are the “D” brackets. In a D bracket, two of the legs of the standard Y bracket are closed in making a shape that resembles a letter D. Less common is what I call the “triangle” bracket shown on the True burner below. The standard Y bracket is made thicker and heavier and taller and then a brace is placed between each leg of the Y.

I have had both D and triangle bracket elements at various times and both seem to be strong enough to support my canners.

The canners take too long to reach temperature

Manufacturers do not always ship their stoves with the highest wattage burners available. To my knowledge the typical wattages for large electric coil burners are 2150 watts or 2600 watts. (Small burners are 1250 or 1500 watts from my research.) I have found that the extra 450 watts provided by by a 2600 watt burner is noticeable. The extra wattage allows for faster heating. All the burners I’ve listed below are supposed to be rated at 2600 watts (I’ve not confirmed this for the Range Kleen).

Below I have compiled a list of all the canning burners that I could track down at the time of this posting (December 2013) complete with as many interchangeable part numbers as I could find.

DISCLAIMER: Check with the manufacturer of your stove to determine if you may safely upgrade your burners and how to do so – don’t just take the advice of some internet blogger whom you randomly discovered via a Google search!

Amazon ImageTrue – triangle bracket – Frigidaire 08011324 also part numbers K1167879, K001167879, 363110, AH413034, EA413034, PS413034, 8011324

Amazon ImageJenn-Air Big Pot CE1 – D-Bracket – Whirlpool YA145A also part numbers 703041, A145A, 704463, 712429, 7-3041, 7-4463, 7-12429, Y703041, 1247494, AH2202791, EA2202791, PS2202791, Y704463, Y712429

Amazon ImageGE WB30k5019 – D-Bracket – also 336177, 4337683, 80650, 257579, AH243843, EA243843, PS243843, 326786

Amazon ImageRange Kleen Canning Burner Kit 102AM7383 – D-Bracket – with drip pan

MP26KA – D-bracket – also MP26KA, TS5C8226, TS5C8226PB, YMP26KA, ERS58D26-CAN, 81410610

Three-pressure Canner Weight Sets

Tired of babysitting your pressure canner? Buy a three-pressure weight!

Traditional dial-gauge canners require you to baby-sit them and continually adjust the heat to maintain the pressure. You’ll think you have it correct and then it’ll start climbing again! Or worse, it’ll drop and you have to start all over, possibly turning your food to mush. All that fluctuating pressure can lead to your liquid syphoning out of your jars. A three-pressure weight set will help! It’s much easier to listen to the weight jiggle while you are cleaning up the kitchen – or sitting on the couch. With a three-pressure weight set, the the exact heat setting under the canner isn’t quite so critical, so it’s much easier to maintain. A more even pressure keeps the syphoning to a minimum. Did I mention you can sit on the couch?

Mirro's equivalent to Presto's three-piece weight set


Mirro has shipped with its canners for years a weight that is capable of the three different pressures that the USDA requires for the definition of a canner. Presto and All-American haven’t always done this. I do not have any Mirro canners, but it is my understanding that the newest ones are shipping with three separate weights rather than the “hockey-puck” style shown here. This hockey-puck style weight “jiggles” every few seconds to maintain the proper pressure.


All-American’s older models shipped without a three-pressure weight. You had to constantly adjust the heat of your burner under your canner to maintain the proper pressure according to the dial-gauge.

Their newer canners ship with a weight that is very similar in design to the old Mirro setup. You can buy the parts to retrofit your older model.

This weight also “jiggles” only every few seconds.

Traditional 15 pound pressure weight Presto

Presto’s traditional weight is a 15 pound regulator. As with the older All-American canners, you had to constantly adjust the heat under your canner to maintain the proper pressure. (Of course, if you need to can at 15 pounds pressure, you can use this weight as-is.) Presto has a a three-piece weight set available for its canners. This weight set allows you to choose a set pressure of five, ten or fifteen pounds. The Presto weights will rock gently when you’ve reached your set pressure.

Presto’s Traditional 15 Pound Pressure WeightTraditional 15 pound pressure weight

Presto’s Three-piece Weight SetPresto's Three-piece Weight Set

The three-piece weight set, set up for 10 pounds pressure.Presto's three-piece weight set, setup for 10 pounds pressure

The three-piece weight set, set up for 15 pounds pressure.Presto's three-piece weight set, setup for 15 pounds pressure

This is the Mirro version of the Presto three-piece weight set. All-American’s weight is very similar to this. Mirro's equivalent to Presto's three-piece weight set

A brief video of the Presto three-piece weight set in action:


The traditional Presto 15lb weight:Amazon Image

Amazon Image

The Presto 3-pressure weight set: Amazon Image

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The Mirro 3-pressure weight: Amazon Image Amazon Image The All-American 3-pressure weight: Amazon Image Amazon Image