the little rubber overpressure plug on my lid popped out and now it won't stay in, it just falls right through the hole

Diagnosis

The issue is caused by the degradation of the elastomeric material in the Safety Overpressure Plug. This plug is a critical fail-safe designed to pop out of the lid if the pressure regulator fails and the internal pressure exceeds safe operating limits. Over time, repeated exposure to high heat (reaching 240°F/115°C during pressure canning) and the caustic nature of some foods cause the rubber to either shrink, warp, or lose its structural integrity. When the plug "falls right through," it means the diameter of the rubber has contracted or the material has become so brittle/deformed that it can no longer maintain a friction fit against the metal rim of the vent hole. You can confirm this by inspecting the plug for visible cracks, a flattened top, or a diameter that appears slightly smaller than the hole in the lid. If the plug does not sit firmly and resist a gentle push from the bottom, the seal is compromised, and the canner cannot safely reach or maintain the required pressure for sterilization.

How to Fix It

You must replace the plug with a genuine Presto replacement part. Do not attempt to "stretch" the old plug or use adhesives, as this can prevent the plug from blowing out during an actual overpressure event, creating a dangerous explosion risk.

1. Purchase the Presto Replacement Overpressure Plug (Part #01781-OP). Ensure you are getting the specific plug for the 23-Quart model, as plugs for smaller Presto cookers may have different tolerances.
2. Thoroughly clean the overpressure vent hole in the lid using a damp cloth and a soft brush. Remove any carbonized food residue or mineral deposits that may be preventing the new plug from seating properly.
3. Inspect the rim of the hole for any burrs or jagged metal edges. If the metal is deformed, the plug will not seal.
4. Insert the new rubber plug into the hole from the top of the lid. Press firmly until the plug is flush with the lid surface.
5. Gently tug on the plug to ensure it is seated securely and does not slide through the hole under its own weight.
6. Perform a "water test" by filling the canner halfway with water and heating it to ensure the plug remains seated until the pressure regulator begins to vent.

If That Didn't Work

• Inspect for Lid Warping: If a brand new plug still falls through, the lid itself may be warped. Place the lid on a perfectly flat surface (like a granite countertop). If the lid rocks or there is a visible gap near the vent hole, the metal has stretched. In this case, the entire lid must be replaced to ensure a safe seal.
• Check for Chemical Degradation: If you have used high-acid foods or strong cleaning agents inside the canner, the metal rim of the hole may have corroded. Use a fine-grit sandpaper (400 grit) to lightly clean the interior rim of the hole to remove oxidation before inserting a new plug.
• Verify Part Authenticity: Ensure you are not using a generic "universal" plug. Generic rubber plugs often vary by 1-2 millimeters, which is enough to cause them to fall through the Presto 01781's precision-drilled hole. Only use OEM Presto parts.

Heads Up

• Annual Replacement: Treat the overpressure plug and the main lid gasket as consumables. Replace them every 12 months regardless of appearance to prevent mid-cycle failures.
• Avoid Overfilling: Never fill the canner past the "Max Fill" line. Overfilling can lead to food particles clogging the vent, which forces the overpressure plug to pop prematurely.
• Storage Tip: Store your canner lid inverted or slightly ajar. Storing it tightly clamped for months can put unnecessary stress on the rubber components and accelerate degradation.
• Visual Inspection: Every time you prep the canner, visually inspect the plug for "mushrooming" (where the top becomes wider than the base), which indicates the rubber is failing.