Explain the hot-water needs
Describe the property, occupants, usage patterns and existing equipment. Ask how the plumber assessed capacity, location and suitability instead of choosing from a headline size or efficiency claim alone.
Ask what the installation covers
Ask which work is included for connections, controls, drainage, removal and making good. Fuel type, location and equipment design can change the scope; ask about relevant local approvals and specialist qualifications.
Agree testing and handover
Request the exact model, operating instructions, warranty terms and maintenance requirements. Ask who arranges registration or inspections when relevant. Compare complete plumbing quotes before agreeing work.