The pressure lock seals the water tank as the pressure inside the water tank increases. This is a particularly important safety feature, as it prevents the user from opening the safety cap when the water tank is under pressure. The pressure seal is a wearing part and the function of the lock itself may be impaired due to limescale build-up. Replacement requires tools, the body must be threaded inside the tank through the hole in the filler neck.
Recycle the pressure lock as a metal waste.