The answer to 'pressure regulator constantly running' is that the pressure regulator is likely malfunctioning and needs to be repaired or replaced. A constantly running pressure regulator can be caused by a faulty diaphragm, a stuck valve, or other internal issues. This can lead to excessive water pressure in the home, which can damage plumbing fixtures and appliances.
In most cases, the pressure regulator will need to be replaced by a professional plumber. Attempting to repair or adjust the regulator yourself can be dangerous and may cause further damage. A plumber can properly diagnose the issue, shut off the water supply, and install a new pressure regulator to restore normal water pressure in your home.