Start with the existing system
Note the system type, model and age if you know them. Describe the fault and any recent repairs.
Think about everyday demand
The number of people, bathrooms and busy times of day all help inform system selection.
Compare the full installation
Ask what the estimate includes: equipment, access, connections, removal, commissioning and any other trade work.
Ask about ongoing care
Discuss operation, maintenance, manufacturer information and what to do if a fault appears after installation.