1. Observe and protect
Document the symptoms, prevent additional damage if it's safe to do so, and gather relevant history on the system.
2. Evaluate the house and site
A sound diagnosis works through fixture behavior, pipe material, water pressure, drainage and venting layout, shutoff locations, physical access, and any repair history already on file.
3. Define a written scope
A written scope should spell out preparation, protection, materials, access, permits, testing, cleanup, finish restoration, exclusions, and change-order rules.
4. Compare providers
Compare credentials along with the reasoning and boundaries behind each proposal -- not just the total at the bottom.
5. Inspect closeout
Confirm testing, cleanup, documentation, warranties, and any remaining maintenance responsibilities at closeout.