The answer to 'why is my pressure regulator slow draining' is that a clogged or malfunctioning pressure regulator can cause slow draining. This is often due to sediment buildup or a faulty diaphragm inside the regulator. A slow draining regulator can lead to low water pressure and other plumbing issues throughout your home.
Some common symptoms of a slow draining pressure regulator include low water pressure, water that takes a long time to drain, and a regulator that doesn't seem to be functioning properly. To fix the issue, you may need to clean or replace the regulator, which is a job best handled by a professional plumber unless you have experience working with these components.