Why will my pressure cooker not come up to pressure?

A pressure cooker builds pressure only when steam is generated faster than it escapes. Every failure to come up to pressure is therefore either not enough steam being made or too much getting out, and where the escaping steam appears tells you which. That single observation shortcuts most of the diagnosis.

Safety

What you'll need

• The manual for your specific model
• A spare sealing ring, if yours is more than a year or two old (optional)
• A soft brush and warm soapy water

Step by step

1. Watch where the steam escapes and note it.Steam from around the rim points at the seal. Steam continuously from the regulator points at the valve setting. No steam and a quiet pot points at liquid. Nothing happening at all points at the lid not being locked. Everything below follows from this.
2. Check the regulator is set to seal, not vent.On many electric cookers this is a small switch on top with two positions, and on stovetop models the weight has to be seated on the vent pipe. Leaving it on venting is the single most common cause and it costs nothing to check.
3. Check the lid is turned fully to its stop.A partly turned lid does not engage the lugs and, on an electric model, will usually refuse to start the pressure cycle at all. Turn it until it stops and, on models with an alignment arrow, until the arrows line up.
4. Inspect and reseat the sealing ring.Take it out and put it back, seated evenly all the way round its channel and not twisted or stretched. Check it is not hardened, cracked or greasy. A ring that has gone hard no longer conforms to the rim and is the most common physical cause. Rings are consumables and should be replaced every year or two of regular use.
5. Confirm there is enough liquid.Pressure is made of steam and steam is made of water. Most models need at least 250ml, and more for a long cook. A thick sauce or a dish with all its liquid absorbed by rice or pulses will never build pressure, and the same conditions will scorch the base.
6. Check the vent pipe and the safety valve are clear.Cold and empty, look up into the vent and at the safety valve on the underside of the lid. Food debris there gives erratic behaviour. Clear with warm soapy water and a soft brush, and never with anything that could widen the opening.
7. Check the rim of the pot for damage.A dented or distorted rim on a stovetop cooker will not seal whatever the ring is doing. Sight along it. A dented cooker is retired, not straightened.
8. Check the heat if it is a stovetop model.A large stovetop cooker on a small ring will take a very long time to build pressure or never get there. Use a ring that matches the base diameter, on high, until the regulator shows pressure, then reduce it to hold.

Tips

• Keep a spare sealing ring. They perish, they take on the smell of whatever you cooked, and having a second lets you keep one for savoury and one for sweet as well as covering a failure.
• Store the cooker with the lid inverted on the pot rather than locked on. A ring compressed in a closed lid for months deforms and stops sealing.
• If your electric cooker shows a burn or overheat message rather than building pressure, that is thin liquid scorching on the base. Deglaze the base before starting the pressure cycle.
• Time from when pressure is reached, not from when you switch it on. A cooker that takes fifteen minutes to come up has not started cooking during those fifteen minutes.

Common mistakes

• Greasing or stretching the sealing ring to make it fit — It is a compression seal that works by conforming to the rim. Stretching it permanently deforms it, and oil on it attracts debris and accelerates perishing.
• Trying to force or lever a lid — The lock is a safety mechanism and it is holding because there is pressure inside. Wait for the float to drop; there is no situation in which forcing is the right response.
• Filling above the limits to make a bigger batch — Over two-thirds, or over half for foaming food, there is not enough headspace and foam reaches the vent. A blocked vent is how the safety systems get tested for real.

If it doesn't work