Sustainable Use of Water (Leaving Cert Construction Studies): Revision Notes
Sustainable use of water
Understanding water sustainability
Water represents a valuable natural resource that requires careful management in modern homes. With the introduction of water metres across many areas, households now face direct costs for their water consumption. This creates both environmental and economic incentives to use water more efficiently.
The concept of sustainable water use focuses on meeting current water needs whilst ensuring adequate supplies remain available for future generations. In domestic settings, this involves reducing unnecessary consumption and exploring alternative water sources for appropriate applications.
Water conservation methods
Several practical approaches can significantly reduce household water consumption without compromising comfort or hygiene standards.
Toilet efficiency improvements
Dual flush toilet systems offer variable water volumes depending on waste type. These systems typically use around 3 litres for liquid waste and 6 litres for solid waste, compared to older single-flush systems that may use 9-11 litres per flush regardless of need.
Kitchen and bathroom practices
Simple behavioural changes deliver substantial water savings. Avoiding overfilling kettles reduces both water waste and energy consumption. Choosing showers instead of baths generally uses less water, particularly for shorter shower durations.
Practical Water-Saving Tips:
- Turn off taps whilst brushing teeth - saves up to 6 litres per minute
- Take 4-minute showers instead of baths - saves approximately 35 litres per use
- Only run dishwashers and washing machines with full loads
- Fix dripping taps immediately - a single drip can waste over 5,000 litres annually
Turning off taps when not actively needed prevents significant waste. Examples include switching off taps whilst brushing teeth, washing dishes, or performing other cleaning tasks that don't require continuous water flow.
Rainwater harvesting systems
Rainwater harvesting provides an alternative water source for specific domestic applications. This approach captures precipitation that would otherwise flow into drainage systems and makes it available for household use.
What rainwater harvesting involves
The process centres on collecting rainfall from roof surfaces and redirecting it through guttering systems into storage facilities. The collected water undergoes basic filtration before being made available for redistribution around the property.
It's crucial to understand that harvested rainwater is non-potable, meaning it's not safe for drinking or food preparation. Systems must therefore be designed to prevent any connection with taps or appliances used for potable water supplies.
Applications for harvested rainwater
Rainwater proves suitable for several household functions that don't require drinking-quality water:
Toilet flushing represents the largest potential application, as toilets typically account for around 30% of household water consumption. Since flushing requires no special water quality, rainwater provides an ideal substitute.
Clothes washing in washing machines can utilise harvested rainwater effectively. Modern washing machines work efficiently with rainwater, though users should monitor for any mineral buildup over extended periods.
Garden irrigation benefits significantly from rainwater use, as many plants actually prefer rainwater to treated mains water. The absence of chlorine and other treatment chemicals can improve plant health.
External applications such as outside taps for car washing, patio cleaning, or other outdoor tasks suit rainwater perfectly.
These applications represent the ideal uses for rainwater because they don't require the high quality standards needed for drinking water, yet they account for a significant portion of typical household water consumption.
System components and operation
A complete rainwater harvesting system includes several key elements working together.
Collection occurs through existing roof guttering, which channels water from the roof surface towards the storage system. The roof essentially functions as a large collection surface, with gutters acting as the primary gathering mechanism.
Filtration removes organic matter and debris before storage. Basic philtres screen out leaves, twigs, and other materials that could contaminate the stored water or block system components.
System Component Overview:
Step 1: Collection
- Roof acts as catchment area
- Gutters channel water to downpipes
Step 2: Filtration
- First-flush diverters remove initial dirty water
- Mesh philtres catch leaves and debris
Step 3: Storage
- Cisterns hold 135-230 litres typically
- Located in roof spaces or elevated positions
Step 4: Distribution
- Pump systems maintain pressure
- Separate pipe network prevents contamination
Storage tanks hold the filtered rainwater until needed. These cisterns are typically located in roof spaces or other elevated positions to provide adequate pressure for distribution. Common storage capacities range from 135 to 230 litres, depending on household requirements and available space.
Pump systems deliver stored water back to appropriate points throughout the house. The pump activates automatically when taps connected to the rainwater system are opened, maintaining adequate pressure for normal use.
Integration with existing plumbing
Rainwater systems connect to cold water supplies through separate pipe networks. This separation ensures no cross-contamination between potable and non-potable supplies.
The harvested water feeds designated outlets such as toilet cisterns, washing machine connections, and external taps. Pipe sizes typically use 15mm diameter for branch connections and 22mm for main distribution runs.
Overflow provisions handle periods when storage capacity is exceeded during heavy rainfall, directing excess water safely away from the building structure.
Safety and regulatory considerations
Proper system design prevents any possibility of rainwater entering the drinking water supply. This requires complete separation of rainwater and mains water systems, with appropriate labelling of all non-potable outlets.
Critical Safety Requirements:
- Never connect rainwater systems to drinking water taps
- Clearly label all rainwater outlets as "Non-Potable Water"
- Install backflow prevention devices
- Regular maintenance of philtres and storage tanks ensures water quality remains suitable for intended applications
Users should inspect and clean philtres periodically and check storage tanks for any signs of contamination or damage.
Key Points to Remember:
- Water conservation saves money through reduced bills and helps protect environmental resources
- Simple changes like dual flush toilets, shorter showers, and turning off taps create significant savings
- Rainwater harvesting captures free water from roofs for non-drinking applications
- Harvested rainwater works well for toilet flushing, washing clothes, gardening, and outdoor cleaning
- Proper system design keeps rainwater completely separatefrom drinking water supplies to ensure safety