The answer to 'why is my boiler smells bad' is that a smelly boiler is often caused by a buildup of sludge, rust, or other debris in the system. This can lead to a foul odor, especially when the boiler is running. Common symptoms include a rotten egg or sulfur-like smell, as well as discolored or dirty water coming from the taps.
In many cases, the solution is to have the boiler professionally serviced and flushed to remove any buildup. This may involve draining the system, cleaning the internal components, and treating the water to prevent future issues. Neglecting a smelly boiler can lead to more serious problems, so it's best to address the issue as soon as possible.