Waste Water Recovery Systems WWRS

[edit] Introduction

A Waste Water Heat Recovery Systems (WWHRS) is a some what lesser known technology, that focusses on reclaiming the thermal energy, typically lost when warm or hot wastewater, such as from showers, dishwashers, and washing machines is discharged. Recovering the heat from this waste run off can save on energy demand for water heating, lower carbon emissions, and cut utility costs.

Typically, the hot water from a shower quickly goes down the drain at a temperature of around 30–40°C, while new cold water enters the system at roughly 10°C. The heat in the wastewater is valuable energy that is effectively wasted. WWHRSs use a heat exchanger to transfer this waste heat from the outgoing warm wastewater, either directly to the incoming cold water or to the storage tank. This waste heat when exchanged to the incoming water preheats it, raising it from around 10°C to 20–25°C, so requiring significantly less energy to reach the 30–40°C required for the shower. As the temperature is doubled the reductions in energy required can be around 50–60%.

[edit] Different types of Water Heat Recovery System

Most systems comprise of two main components:

• A heat exchanger – where warm wastewater and cold mains water are in separate but adjacent areas. Heat transfers from the warm side to the cold side.
• Pipework and controls – To direct wastewater from the shower drain and incoming mains water through the system at optimal flow rates.

The paper 'Waste Water Heat Recovery Systems types and applications: Comprehensive review, critical analysis, and potential recommendations' describes systems as being classified by structure and configuration thus:

• Structure
  • Vertical - Falling-film heat exchanger, usually part of the waste piping system.
  • Horizontal - Counter flow-shell and tube heat exchanger, part of the shower base.
  • Oriented - Falling-film heat exchanger with a tilt angle,
  • Storage tank - Internal coil with a storage tank
• Configuration
  • Coupled to a Heat pump ar a Solar system
  • Non-coupled

In simple terms the four systems might be simply described as:

1. Vertical (Drainpipe) WWHRS

• Description: The most common domestic system, often installed in multi-storey homes.
• Operation: Wastewater flows down a vertical copper or stainless-steel pipe containing a counterflow of incoming mains water.
• Advantages: Simple design, high efficiency (up to 60% recovery), minimal maintenance.
• Limitations: Requires sufficient vertical space (usually installed under a first-floor shower).

2. Horizontal (Shower Tray) WWHRS

• Description: Designed for installations where vertical space is limited.
• Operation: The system sits beneath the shower tray, with a heat exchanger plate that the wastewater runs across, transferring heat to a cold-water coil beneath.
• Advantages: Compact and ideal for ground-floor or apartment installations.
• Limitations: Typically less efficient (30–45%) compared to vertical units.

3. Storage-Based (Tank) WWHRS

• Description: Used in larger or commercial setups. These systems collect warm wastewater in a storage tank before transferring the heat to incoming cold water via a heat exchanger.
• Advantages: Can recover heat from multiple sources (e.g., showers, dishwashers, laundry).
• Limitations: Larger footprint, more complex plumbing, and maintenance requirements.

4. Instantaneous or Direct Flow Systems

• Description: These systems recover heat in real time as water flows through them, without storage.
• Advantages: Continuous operation, immediate efficiency.
• Limitations: Best suited to consistent water use, such as in hotels or gyms.

[edit] Benefits of WWHRS

• Energy savings: Up to 50–60% of the heat energy from shower wastewater can be recovered.
• Reduced carbon footprint: Less energy use means lower CO₂ emissions.
• Cost efficiency: Lower energy bills and minimal maintenance once installed.
• Compatibility: Works with most hot water systems, including boilers and heat pumps.
• Sustainability: Supports green building standards (e.g., BREEAM, SAP ratings).

[edit] Development History

While the principle of heat recovery dates back over a century, the modern domestic Waste Water Heat Recovery System as used today was pioneered in the early 2000s. One of the early innovators in the field was Hans van der Meer, a Dutch engineer who developed one of the first commercial versions of a vertical shower drain heat recovery unit in the Netherlands around 2004. His design, later marketed under names like Showersave and Recoh-Vert, became a model for similar technologies across Europe. Subsequently, other manufacturers such as Power-Pipe (Canada) and Recoup Energy Solutions (UK) refined the concept for different building types and national regulations.

[edit] Conclusion

Waste Water Heat Recovery Systems represent an elegant and practical solution to one of the most overlooked inefficiencies in buildings: the loss of thermal energy through drains. By reclaiming this energy and reusing it to preheat incoming water, WWHRS can cut domestic hot water energy use by up to half, reduce emissions, and contribute significantly to sustainability goals. Whether in homes, hotels, or industrial facilities, these systems embody the growing trend of making our infrastructure smarter, greener, and more efficient—one shower at a time.

[edit] Related articles on Designing Buildings

• Air conditioning.
• Air handling unit.
• Chiller unit.
• Coefficient of Performance CoP.
• District energy.
• Ecobuild 2016 - Making the business case for large scale retrofit investment.
• Exhaust air heat pump.
• Geothermal pile foundations.
• Gross calorific value.
• Heat exchanger.
• Heat pump.
• Heat recovery ventilation.
• Heat recovery for buildings.
• Heat source.
• Heating.
• HVAC.
• Mechanical ventilation.
• Mechanical ventilation's role in improving indoor air quality.
• Refrigerants.
• Tempering heating.
• Types of heating system.
• Types of heat exchanger.
• Variable refrigerant flow.
• Waste heat.
• Waste water.
• Zero Bills Home.

[edit] External links

https://www.sciencedirect.com/science/article/pii/S2352484723009861#sec3

https://recoup.co.uk/products/pipe-hex-range/