> pressurized plumbing that you really don't want to DIY

They're fine to DIY if you're sensible about it. If you can build it, you can build a simple hydrostatic pressure tester. Pump, valves, tubes and a gauge. No computer parts. Pump the tank up to 1.5x rated pressure. This is industry standard.

But of course the age old saying applies: know what you're doing.