Replacing water heater anode
The anode in your water heater should be inspected several times per year, depending on how often you are using your water heater. We live in ours full-time, so it really makes sense to inspect the anode every 3-6 months.
I took a look at ours today and it was getting quite worn. There was certainly still material left. However, there was an area where the magnesium was eroded away down to the steel that forms the rod. So, I replaced it. Ours takes a 9-1/4 x 3/4 magnesium anode rod.
Some tips for preparing for a replacement:
Safety first!
Turn your water heater off the evening before, to let it start cooling.
By washing dishes, showering, etc., use up as much of the hot water as possible.
Before removing the anode, continue to run water from your hot water supply to convince yourself that the water has cooled. You do NOT want to be scalded.
Before removing the anode, turn off your water supply. If you leave it on, once you remove the anode, your system will start trying to fill your water heater. As part of the procedure, you want to actually drain your heater.
Turn off the hard on/off switch (if your heater has one) in addition to your control panel where you shut off the heater the night before.
Open your pressure relief valve. This will allow the heater to drain when you remove the anode.
When you remove the anode, take a step back. Water will come out and you might get wet.