Services and Sustainability
Services and Sustainability tests water, drainage, wastewater and low-energy servicing, with an emphasis on whole-system thinking. Expect supply, storage, harvesting, treatment, drainage and renewable heat.
Core rules
- Water supply needs pressure, storage and backflow protection; potable and non-potable supplies must be kept separate.
- Rainwater harvesting needs a collection area, first-flush diversion, filter, tank and overflow.
- Wastewater may go to a sewer or an on-site system; a percolation test checks whether the ground can accept treated effluent.
- Sustainable drainage slows runoff using soakaways, permeable paving and attenuation.
- Heat pumps produce low-temperature heat and work best with high insulation and large emitters.
Worked example
A roof collects from 100 m²; annual rainfall is 1,000 mm; runoff coefficient is 0.8. Rainfall depth = 1.0 m. Collectable volume = 100 × 1.0 × 0.8 = 80 m³/yr = 80,000 litres/yr. The reasoning is: area × depth × coefficient, with units kept consistent. This is a supply estimate; tank size depends on demand pattern and dry spells, not annual total alone.
Traps
- Sizing a tank from annual rainfall only.
- Omitting first-flush diversion or overflow.
- Assuming harvested rainwater is automatically potable.
- Ignoring soil percolation for an on-site wastewater system.
Name the source, treatment and disposal route.