To my understanding, backflow preventer testing requirements are dependent on the water authority. For Pittsburgh, it’s likely PWSA. https://www.pgh2o.com/residential-commercial-customers/backflow-device-testing

Every year. It's all part of the Safe Drinking Water Act of 1974.

https://americanbackflowsolutions.com/index.php/a-brief-history-of-backflow-prevention/

Tl/dr: The EPA sets the standards, but it's up to the local purveyor (water supplier) to comply with it.

Lived in the area my whole life. Never did anything like this once, nor do I know of anyone having to do this

That's because it's mostly for commercial/business water lines. The backflow prevention standards are based on hazards on site.

Most, if not all residential buildings have nothing that would require a testable backflow, therefore you wouldn't have to do anything.

Right, thanks for adding that.

So for residential are owners required to do it every year ? Or would that be directed by like a HOA of the community?

If you have a testable backflow prevention device in your home I would believe it would be the responsibility of the homeowner to have it tested.

Do you have any irrigation system or yard sprinklers? That's the only time I've even seen a testable backflow device inside of a house.

I rent commercial warehouse space in Monroeville, every year it needs done. Phil Vento is the man for this stuff. I don't know of anyone that requires it in residential, but there may be some cases...

In order to do a backflip test you have to have a back flow check valve in you’re city water line. It’s to prevent water from siphoning back into the city water system.