Use the heat already leaving through a suitable drain route as a home-specific performance question, with the actual plumbing layout deciding feasibility.
Define the performance outcome
Ask the plumbing designer to identify drain geometry, simultaneous flow conditions and how the proposed heat-recovery unit interfaces with the hot-water supply. Natural Resources Canada describes this as transferring drain-water heat through a heat exchanger to incoming water; suitable application depends on the selected product and installation.
Design around the retained home
The assessment should identify accessible stack length, service access, connection changes and any limits of the existing system. Do not treat a catalogue efficiency figure as a promised household saving. First fitting is a coordinated Installing stage after the improvement design is agreed.
Coordinate the improvement sequence
Agree the assessment and design decisions before ordering products or opening finishes. The completion brief should address selected configuration documented, applicable commissioning checks recorded, access and future care explained. Identify the responsible specialist, preparation, fitting and reinstatement stages. Keep any defect repair separate from the intended improvement so the household can understand what the project changes and what remains.
What shapes the scope?
- Drain and supply layout
- Product and access requirements
- Connection and trade coordination
- Finishing and verification scope
What should be checked?
- Selected configuration documented
- Applicable commissioning checks recorded
- Access and future care explained
Questions worth asking
What makes this an upgrade rather than ordinary renewal?
Adds heat recovery from wastewater, a different function from heating-water equipment replacement or ventilation heat recovery. This brief is for an assessed improvement in capability or performance. Same-role renewal of a failed component belongs at Replacing; first fitting and routine care remain separate Installing and Maintaining stages.
What should the initial proposal explain?
Ask for the intended outcome, existing-condition assumptions and the evidence needed to select a suitable approach. Include drain and supply layout and product and access requirements. The provider should identify design responsibilities, limitations and the checks that make the result assessable without guaranteeing a universal saving or outcome.
Bring the details together.
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