Yes a building permit is legally require for any new water heater change out… even if there is already one there. A building permit is, by design, there to protect you. An improperly installed water heater can do substantial damage to your home or even kill the occupants. Water heaters can explode. Water heaters can leak carbon monoxide in to your attic, and in turn, in to your living quarters. Water heaters can leak flooding your home. There are many potential dangers. Getting a building permit gives you reassurance that your water heater is installed correctly. An experienced building inspector will come to your home to be sure you or your contractor installed your water heater up-to-code. The codes are designed to be sure you are safe.
Another reason to get a building permit to change out your water heater is that evidence of a building permit is often necessary to obtain financing from lending agencies. In addition, fire and liability insurance damages may not be paid in some cases where improvements (ie: water heater replacement) do not meet regulations. Acquiring permits when needed and complying with building inspection’s requirements will help you and your family be better protected.