How to tell it is time to change water heater?

This is an exactly 20 year old water heater working perfectly. Since it is too old i am worried that it will leak water and it will pour from attic to 2nd floor and damage the walls and wooden floor

Where should i look?

If you are that concerned about it just have it replaced.

All water heaters fail, even relatively new ones. Replace it sooner than later. Putting off the inevitable will always cost you way more than you never saved.

It’s in the attic?
Never see that here.

Does it have a catch pan and drain?

Have you ever seen one in the crawl space like this …

Tired Tank.jpg

An auxiliary pan underneath draining to the exterior is a good start good.

I recommend proactively replacing tank type water heaters in attics at 10 years, regardless of their apparent condition when viewed from the exterior. A ruptured tank can overwhelm the pan and drain and cause catastrophic water damage to the living space below.

any elevated appliance that produces or contains water installed by smart hvac techs, plumbers & owners also install a flood stop device that terminates water supply & alarms whenever water leakage is detected

common sense isn’t so common…some have to be told this

There’s a hose connected to the bottom drain plug with no TPV line?? Nice…

Awesome photo!