4ProTech — Illustrative workflow using fictional data One water heater replacement, from call to invoice. Maya Chen asks Summit Field Services to replace a leaking water heater. Maya approves the $1,850 estimate for equipment, materials and installation. Alex Rivera is scheduled for Tuesday, November 10, from 9 to 11 AM. Alex completes the installation and the office closes the original request. Invoice INV-104 links to work order WO-104. Amount due: $1,850. Request a walkthrough at 4protech.com.