What action should be taken if water from the hot water system has a strange odor?

When encountering a strange odor from the hot water system, inspecting the anode rod and the tank for bacterial growth is the most appropriate action. The presence of odors can often be attributed to the growth of bacteria, particularly if the water is stagnant or if the temperature of the water is kept at a level that allows bacterial proliferation.

The anode rod, typically made of magnesium or aluminum, can serve as a breeding ground for bacteria if it becomes corroded or is not functioning properly. Bacteria such as sulfate-reducing bacteria can produce hydrogen sulfide gas, which has a distinctive and unpleasant smell often described as akin to rotten eggs. By inspecting the anode rod, you can identify if it needs replacement or if it is contributing to the odor issue.

In contrast, flushing the entire system or checking for leaks might not address the underlying cause of the odor. While ensuring the system is in good repair and removing any sediment or buildup through flushing might help improve water quality, it doesn’t specifically target bacterial growth. Similarly, while replacing the hot water heater may seem like a solution, it's a more drastic measure that may not be necessary if the issue is localized to the anode rod or the tank environment.