Last updated: August 22, 2026
Every canning season starts with the same question at the stove. There is a big pot of boiling water on one burner and a heavy canner with a lid clamp in the cupboard, and the recipe on the counter has to go into one of them. Jam is obvious. Green beans, chili, salsa and that family recipe for stewed tomatoes are where people hesitate.
This is not a matter of preference or of how experienced you are. The choice is set by the acidity of the food, and the reason is a specific organism that survives a boiling pot. Get the category right and the rest of canning is straightforward. Get it wrong and no amount of care in the kitchen fixes it.
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Quick Answer
Do you need a water bath canner or a pressure canner?
- The dividing line is pH 4.6. The NCHFP puts fruits, pickles, sauerkraut, jams and jellies on the acid side.
- Low acid foods sit above pH 4.6 and include red meats, seafood, poultry and all fresh vegetables except most tomatoes.
- A boiling water canner is for acid foods only. A pressure canner is required for low acid foods.
- Tomatoes and figs are the trap, since the NCHFP notes some now test above pH 4.6 and need acidifying with lemon juice or citric acid.
Bottom line: match the canner to the food’s acidity, and use a tested recipe from the NCHFP or the USDA Complete Guide to Home Canning.
The Line Is pH 4.6, Not Experience
The NCHFP divides canning by acidity. Acid foods at pH 4.6 or lower include fruits, pickles, sauerkraut, jams, jellies, marmalades and fruit butters. Low acid foods above pH 4.6 include red meats, seafood, poultry, milk and all fresh vegetables except most tomatoes. That single number decides which canner comes out of the cupboard.
The reason is Clostridium botulinum. Its spores survive boiling water and can grow inside a sealed jar of low acid food, where they produce botulinum toxin. Acid conditions block that growth, which is why an acid food can be safely processed in a boiling water canner and a jar of green beans cannot.
What Each Canner Actually Reaches
A boiling water canner tops out at the boiling point of water, 212F at sea level, and that is a ceiling no amount of extra time changes. A pressure canner raises the boiling point by trapping steam. The NCHFP specifies operation at 10 to 15 PSIG to reach 240 to 250F, which is the temperature range that destroys the spores.
The scale of the difference is easy to underestimate. The NCHFP notes that processing low acid foods in boiling water instead would require 7 to 11 hours, against 20 to 100 minutes in a pressure canner at the correct temperature. Acid foods, by contrast, are processed for 5 to 85 minutes in a boiling water canner depending on the recipe.
Which Foods Go in Which Canner
Sort by acidity, then by the tested recipe you are following. The table covers the categories rather than individual recipes, because processing times come from the recipe and not from a rule of thumb. Always take times and pressures from the NCHFP or the USDA guide.
| Method | Temperature it reaches | Foods it is for | Where the limit is |
|---|---|---|---|
| Boiling water canner | 212F at sea level | Fruits, jams, jellies, pickles, sauerkraut | Cannot make low acid food safe |
| Pressure canner | 240 to 250F at 10 to 15 PSIG per NCHFP | Vegetables, meats, poultry, seafood, soups | Needs a working gauge and venting |
| Acidified tomatoes | 212F, boiling water canner | Tomatoes with added lemon juice or citric acid | Only with a tested recipe and the acid added |
| Steam canner | Around boiling point | Acid foods only, per tested recipes | Same limits as a boiling water canner |
Tomatoes deserve their own line because they sit right on the boundary. The NCHFP notes that some tomatoes are now known to have pH values slightly above 4.6, and figs the same, so both need acidifying to be safely processed in a boiling water canner. The practical side of that is in citric acid and lemon juice for canning.
The Confusions That Cause Real Trouble
Three mix ups account for most of the unsafe canning done in home kitchens, and all three come from equipment that looks close enough. A pressure cooker is not a pressure canner, an electric multicooker is not either, and open kettle canning is not a processing method at all.
Pressure Cooker, Multicooker, Pressure Canner
A pressure canner is a specific piece of equipment with a gauge or weight, a vent, and a size validated for canning jars. A stovetop pressure cooker and an electric multicooker are not interchangeable with it, and USDA processing recommendations are built on tested canner performance. The differences are laid out in pressure canner against pressure cooker and in why electric multicookers are not canners.
Open kettle canning, where hot food goes into a jar and the lid is expected to seal on its own without processing, is not a safe method for either category. Neither is oven canning. If a family recipe card describes one of those, the food may be worth keeping and the method is not, as covered in what you cannot water bath can.
Altitude Changes the Numbers
Water boils at a lower temperature as elevation rises, so processing at altitude needs adjustment. The NCHFP states that at 1,000 feet or higher you increase the processing time or the canner pressure according to the tested tables. This applies to both methods and it is not optional.
Look up your elevation once and write it on the inside of a cupboard door. Then use the altitude column in the recipe every time, rather than remembering an adjustment you made last season. The full workflow for each method sits in the water bath canning guide and the pressure canning guide.
Which Canner to Buy First
Buy for the food you preserve most. A gardener drowning in cucumbers, apples and berries gets more use from a boiling water canner in the first season. Anyone canning vegetables, broth, chili or meat needs a pressure canner, because no water bath setup makes those jars safe regardless of processing time.
If you expect to do both, a pressure canner can also be used as a boiling water canner for acid foods on many models, with the lid unlocked and the jars covered by water per the recipe. That makes it the more flexible single purchase, at more weight and a higher price. Sizing, gauge type and stove compatibility are covered in the pressure canner guide.
Frequently Asked Questions
Can I water bath can green beans if I process them for longer? No. The NCHFP is explicit that low acid foods need a pressure canner, and notes that boiling water processing of low acid food would take 7 to 11 hours rather than the 20 to 100 minutes a pressure canner needs. Extra time in a boiling pot does not make the jars safe.
Are tomatoes acid or low acid? They sit on the boundary. The NCHFP notes that some tomatoes are now known to test slightly above pH 4.6, which is why tested recipes call for added lemon juice or citric acid before boiling water processing. Follow the recipe’s acid amount exactly.
Can I use my pressure canner for jam? Many pressure canners can be used as a boiling water canner for acid foods with the lid unlocked, following the tested recipe for water depth and time. Check your manual for whether your model supports it before you rely on it.
Do I need to adjust for altitude on both methods? Yes. The NCHFP states that at 1,000 feet and above you increase either the processing time or the canner pressure according to the tables in the recipe. The adjustment differs for boiling water and pressure canning, so use the right column.
What if I am not sure which category a recipe falls into? Then do not can it from that recipe. Find the equivalent in the NCHFP library or the USDA Complete Guide to Home Canning and use their method and times. Mixed recipes such as soups and salsas follow the lowest acidity ingredient, which usually pushes them into pressure canning.
The Bottom Line
Acidity decides the canner. Fruits, jams, pickles and sauerkraut are acid foods and process in a boiling water canner at 212F. Vegetables, meats, poultry and seafood are low acid and need a pressure canner, which the NCHFP specifies at 10 to 15 PSIG to reach 240 to 250F. Tomatoes need acidifying to join the first group. Adjust for altitude above 1,000 feet, take every time and pressure from a tested source, and never treat a pressure cooker or a multicooker as a canner. Read next: choosing a water bath canner, and choosing a pressure canner.