While many homeowners are capable of replacing a water heater on their own, it's generally recommended that the job be done by a licensed professional. That's because water heaters contain a lot of complicated parts, and even a small mistake can lead to serious problems. In addition, there is always the risk of flooding when dealing with water heaters. To be safe, it's best to leave the job to someone who has experience and knows what they're doing. Additionally, most manufacturers void the warranty on water heaters if they are not installed by a licensed professional. So, while it is possible to replace a water heater on your own, it's usually not worth the risk.