On Fri, 7 Dec 2007 12:56:51 -0500, RichK wrote:

"blueman" wrote in message

We have an approximately 4 year old gas-fired 50 gallon hot water
heater.

You do not say what the warranty period is for this heater. If 10y - it may
be to early to change the anode.

However, I could not get the large nut on top of the water heater to
budge. I tried liberally applying liquid wrench and using as much
force as I dared so as not to damage the gas connection.

"As much force" is relative. I'm not sure what the neede torque is, but
it's a lot. I needed an extension on the wrench. With an extension, you
can apply continuous force and it will let go.

Any suggestions on how to loosen the nut?

Just gentle force via an extension.

Instead of a wrench, use a socket and breaker bar.