If your vacuum flask is leaking, there could be several reasons for it. Here are some common causes and solutions:

1. Damaged Seals: Check the seals (rubber gaskets) on the lid and stopper. If they are damaged or worn out, they may not be providing a proper seal. Replace any damaged seals.

2. Loose Lid or Stopper: Ensure that the lid and stopper are tightly closed. If they are not securely fastened, it can lead to leaks. Double-check and tighten them properly.

3. Overfilling: Avoid overfilling the flask, as it can exert pressure on the lid and stopper, potentially causing leaks. Fill the flask only up to its recommended capacity (we recommend filling Energify jars up to the neck).

4. Cracks or Damage: Inspect the flask for any cracks or damage. Even a small crack can compromise its ability to maintain a vacuum, leading to leaks. 

5. Improper Cleaning: Using abrasive materials or harsh chemicals during cleaning can damage the flask's surface and seals. Stick to gentle cleaning methods and avoid using the dishwasher for parts that are not dishwasher-safe (such as the stopper, lid, and silicone rings of Energify jars).

6. Temperature Changes: Extreme temperature changes can affect the vacuum insulation. If you have filled the flask with a hot liquid and then exposed it to a sudden temperature drop, it may cause leaks. To prevent this, preheat the food jar with piping hot water before putting hot food inside or pre-chill it with ice-cold water before adding cold contents.

If the issue persists after checking and addressing these factors, it may be time to consider replacing the flask, especially if it is old or heavily damaged.