Pressure Canner Gauge Testing: Where to Get a Dial Gauge Checked

This is one small errand a year. It is a nice one to get done while your jars are still in the cupboard. It usually means a phone call and a short trip.

What do I need?

• Your canner's lid, or the gauge if the office asks for it alone
• The maker, the model number and the manual for your canner
• Some time before the season starts, because offices get busy and some test by appointment

How do I get it checked?

1. Check what you have

   Look at your canner and its manual. Only a true dial gauge goes in for testing. A weighted gauge needs no accuracy check, says the USDA. If you are not sure which you own, our gauge comparison shows the difference.

2. Find your extension office

   Use the directory of extension offices by state, then look for your county office. Searching your county's name with "pressure canner testing" often brings up the right page.

3. Call first

   Ask whether the office tests gauges, whether it covers your brand, whether you need an appointment, and what to bring. The USDA says "many" offices do this, which means not all.

4. Bring what they ask for

   One office may want the lid with the gauge attached and the gasket, as OSU Extension in Washington County, Ohio does. Another may take the gauge alone. Wrap it well, and do not put it under water.

5. Read the result against the USDA rule

   The USDA says to replace a gauge that is off by more than 2 pounds. For a smaller difference, ask the tester what to do and follow the USDA's advice on adjusting.

6. If no office can help, ask the maker

   Presto's care page describes taking the gauge off carefully, wrapping it and sending it to its Consumer Service Department. For other brands, call the maker and have your model number ready.

Why is this worth doing?

The USDA says gauges that read too high cause under-processing and may leave food unsafe. Low readings cause over-processing. So a gauge that has drifted high can mislead you with no sign at all, since your jars may seal normally.

UGA Extension says that in its example, a 2-pound error can cut the germ-killing effect by 30 percent.

Gauges drift for ordinary reasons. OSU Extension names rough use, knocks, and storage in extreme heat or cold. A seal does not show that the food got hot enough. That is why a yearly check is part of the routine. Our botulism page explains why it matters.

When should it be checked?

The USDA says before use each year. Presto's care page adds these moments, even if your yearly check is done:

• The cover went under water or was dropped
• The gauge glass is broken or missing
• Parts look rusty
• The needle does not rest on zero
• You think it is off

Which gauges can be tested where?

Other dial brands are the gap. If yours is not on the list, ask the maker.

Presto's newsletter also says most of its dial canners can switch to its weighted regulator, part 50332, or kit 85485 on most older models. It calls that an option where there is no testing service. It adds that the altitude cutoffs change, so the dial chart in your manual no longer applies. That is Presto's word about Presto canners. Ask Presto about your model first. See our gauge comparison.

What does testing usually involve?

Terms vary by office, so take these as examples. Illinois Extension says testing is free at the county offices it names, by appointment or drop-off.

University of Wisconsin-Madison Extension says Presto does not charge for its own testing. You pay to mail the gauge, and Presto pays the return. Presto says its unit usually checks a gauge in less than one minute. The unit is not for use at home.

Why is a digital canner different?

A digital canner has no dial and no gauge in this sense. Presto says its sensor reads heat. Its FAQ says the machine is run by electronics and will never need calibration or checking. That is Presto's statement.

The extension pages we read describe dial gauges only. We found none that offers to check a digital canner's sensor, though we did not read every office's page.

A sensor in the canner does not measure heat inside your jars. Presto has not published its jar data. Nobody outside the company has published test results for Presto Precise canners. The Presto Precise page and the digital pressure canner page have more.

What mistakes should I avoid?

• Waiting until the jars are filled. Do it before the season, so a failed gauge does not hold up your harvest.
• Assuming a new canner is exempt. The USDA's yearly rule has no such exception. Ask your maker or office if you want to be sure.
• Testing the wrong part. On a dial canner, the small weight on the vent pipe is not the gauge, says UGA Extension. Our parts page shows what is what.
• Keeping a failed gauge. The USDA says to replace it. When ordering, give your canner's model number and describe the part you need.

What if I am still choosing a canner?

If the yearly errand sounds like too much, the stovetop canner guide covers weighted options too. If you like seeing the needle, this is the dial canner we would start with. Our overview of all machines has the wider picture. The tested recipes page is your next stop once the gauge is sorted.