Start With Where the Odor Occurs
Note whether the odor occurs in hot water only, hot and cold water, one faucet or every fixture, and whether it is constant or intermittent. Those details help narrow the source.
Testing & Diagnosis
Field screening and water chemistry can help distinguish the water source from a plumbing or water-heater issue.
Treatment
Depending on the cause, treatment may use aeration, oxidation, activated carbon or other approaches. A water-heater source may require a different correction than a well-water source.