my canner's overpressure plug is kinda melted and deformed, do i need to worry about it or can i just keep using it?

Diagnosis

The overpressure plug on your Presto 01755 is a critical safety fuse designed to prevent the pressure canner from becoming a catastrophic projectile. This plug is made of a specific low-melting-point alloy that is engineered to liquefy or deform at a precise temperature and pressure threshold. If the plug is already melted or deformed, it means the safety mechanism has been triggered—either by a previous overpressure event or by prolonged exposure to extreme heat—and the structural integrity of the seal is now compromised.

When this plug is deformed, it can no longer provide a reliable seal, leading to "steam leaks" that prevent the canner from reaching the required 11 PSI (or the specific pressure needed for your altitude). More dangerously, if the plug has partially melted, it may not blow out correctly during a genuine emergency, or it may fail prematurely, causing a sudden, violent release of steam that can cause severe burns. You can confirm the failure by inspecting the plug for a concave dip, discoloration, or a "bubbled" appearance on the metal surface. If the plug is not perfectly flush and circular, it is functionally dead.

How to Fix It

You must replace the overpressure plug before the next use. Do not attempt to hammer it flat or seal it with adhesives, as this creates a bomb-like scenario by removing the only failsafe in the lid. Follow these exact steps to replace it:

1. Procure the Correct Part: Purchase a genuine Presto Overpressure Plug specifically compatible with the 16-quart aluminum series. Avoid generic "universal" plugs as the tolerances for the 01755 lid are precise.
2. Remove the Damaged Plug: Turn the canner lid upside down. Locate the overpressure plug (the small metal disc). Using a blunt tool, such as the handle of a screwdriver or a wooden dowel, apply firm, steady pressure to the center of the deformed plug to push it out of the lid housing.
3. Clear the Seat: Use a damp cloth and a small brush to clean the aperture where the plug sat. Ensure there are no remnants of melted alloy or food debris clinging to the rim of the hole, as this will prevent the new plug from seating properly.
4. Insert New Plug: Place the new plug into the hole. Press it firmly with your thumb until you feel it "snap" or seat fully into the housing. It should be flush with the lid surface.
5. Verify Seal: Before loading the canner, perform a "dry run" by filling it with water and heating it to see if steam escapes from the plug area before the pressure regulator begins to vent.

If That Didn't Work

• Check the Lid Gasket: If you replaced the plug but the canner still won't reach pressure, your rubber gasket is likely the culprit. Inspect the gasket for cracks or "flattening." If it is over two years old, replace it with a new Presto 16-quart gasket to ensure a vacuum-tight seal.
• Inspect the Vent Pipe: A melted plug is often a symptom of a clogged vent pipe. Use a pipe cleaner or a thin wire to ensure the vent pipe (the tube the regulator sits on) is completely clear of debris. If the pipe is blocked, pressure builds up internally, forcing the overpressure plug to melt.
• Examine the Pressure Regulator: Ensure your regulator weight is not dented or corroded. A damaged regulator can cause the internal pressure to spike beyond the rated limit, which is exactly what triggers the overpressure plug to deform.
• Check for Lid Warping: If the plug continues to leak or deform despite replacement, place the lid on a flat granite countertop. If the lid rocks or doesn't sit flush, the aluminum has warped, and the entire lid assembly must be replaced for safety.

Heads Up

• Never Force the Lid: If the canner is difficult to lock, do not force it; ensure the gasket is seated correctly to avoid uneven pressure distribution.
• Altitude Adjustment: If you live at high altitudes, remember that your boiling point is lower; always use the correct weights to prevent over-pressurizing the system.
• Avoid Overfilling: Never fill the canner more than 3/4 full. Overfilling can lead to liquid being pushed into the vent pipe, causing a blockage that will melt your overpressure plug instantly.
• Visual Inspection: Make it a habit to inspect the overpressure plug every 5-10 uses. If you see any pitting or discoloration, replace it proactively.