When using a spirit level it is important to remember that it is a precision instrument and can become inaccurate if it is treated roughly or accidentally dropped.

Before purchasing a level you can use the following steps to make sure it is not faulty.

If you already own one, it is wise to occasionally check the vial’s accuracy.

How to Check a Spirit Level for Accuracy.

Horizontal

1. Place the level on a flat surface and make a mark to show where the level is sitting.
2. Note the exact position of the bubble in the vial.
3. Turn the level over to the other side and place it against the mark you made.
4. Check the exact position of the bubble in the vial again.
5. If the bubble has returned to the same place, the level is accurate.  If it didn’t, then it may be inaccurate.  Always double check by repeating the process above.

Vertical

1. To check the "plumb" or "vertical" vials, place the level against a door frame or wall.
2. Make a mark on the wall beside the top vial.
3. Note the exact position of the bubble in the vial.
4. Turn the level over to the other side and place it against the mark you made.
5. Read the level again and note its exact position in the vial.
6. Check the exact position of the bubble in the vial again.
7. If the bubble has returned to the same place, the level is accurate.  If it didn’t, then it may be inaccurate. Always double check by repeating the process above.