Here is a situation where the homeowner must understand the technical difference between Pluming & Maintenance.

Plumbing is defined as the act of initially installing or altering an existing system.

Maintenance is defined as physically repairing or maintaining an existing system provided you do not alter the original layout or increase loads.

In nearly all jurisdictions the property owner or his/her delegated representatives may perform maintenance.

If you are removing a defective WH and replacing it with the same type and size of WH that is a maintenance activity but, even when performing maintenance you are required to make the installation in accordance with existing codes at the time of the change.

Generally maintenance does not require a permit, but check with your local AHJ because many areas are now requiring permits for WH.

I have lived in a number of jurisdictions that will only allow the replacement of faucet washers without a permit.

They do not inspect most of the time (even if a permit IS pulled) though, and homeowners routinely thumbs there nose at them and do work.

In my locale a permit is required to install OR replace a WH whether NG, LP, or electric. A mini-test is available for a homeowner to qualify to replace a WH, but not the gas part so you still need a plumber with a gas ticket for that. A permit IS required. Most licensed plumbers around here do not pull permits to replace a WH and are in violation of their license but that's another story.

A ways back there was a local guy who didn't pull a permit to replace his water heater and didn't get a licensed plumber with a gas ticket to do the job. There was an explosion in his garage after a period of time and his homeowner's insurance did not pay the claim. The guy took the insurance company to court and lost.

The morale of the story is to check with YOUR local authority regarding regarding the requirements and permits necessary and then YOU KNOW. As rarely as homeowner's need to replace WHers the cost of a plumber is amortized over a (hopefully) long period of time and it's just something it is smarter to do in case something goes wrong.

"There was an explosion in his garage after a period of time and his homeowner's insurance did not pay the claim. The guy took the insurance company to court and lost. "

Every time I have actually checked into the details of "insurance did not pay" it has proven incorrect.

Unless there is a specific exclusion in a policy you are insured for your own mistakes.

Every time? IIRC the Fire Marshal determined that the gas line connection to the water heater contributed to the explosion. It was a new water heater and the homeowner could not provide a receipt from a licensed plumber for installation or a permit. In this locale a permit is required for water heater replacement. The insurance company did not pay the claim and the court agreed.