Uh, no it's not. It is a Maxiumum level mark, which is why it reads,
"Do not immerse beyond water mark." It seems most people choose to
ignore it, though.
Cris

On Fri, 12 Dec 2003 03:53:40 -0500, Dr. Know
wrote:

This is the MINIMUM water level mark. This is the level at which they
MUST be submerged to in order to be accurate and avoid cracking the
heater tube.

Greg