Cold Water Supply (Leaving Cert Construction Studies): Revision Notes
Cold water supply
Overview of water distribution
Water reaches your home through a mains pipe connection. This connection sits in a chamber beneath the pavement outside the property. From this point, water travels directly to the kitchen sink through the main supply pipe.
Key components in the water distribution system include stop valves and drain valves. Stop valves control water flow and sit at connection points to the mains pipe outside the property and beneath the sink. Drain valves install above the stop valves to allow water drainage from the system when maintenance is required.
Stop valves and drain valves are essential components for system maintenance and emergency shutoff. Always locate these valves before beginning any plumbing work.
Pipe fittings and connections
Fittings serve as connectors between different sections of pipework. These components come in various shapes and sizes, manufactured from materials including plastic, copper and cast iron. Their primary functions involve splitting connections, changing pipe direction, and extending pipework systems.
Modern plumbing systems use fittings to connect sinks to the main water supply, ensuring proper water distribution throughout the property.
Cold water supply systems
Two main systems deliver cold water to residential properties: direct and indirect supply systems. Each approach offers distinct benefits and limitations.
Direct cold water supply system
The direct system connects the mains feed directly to all household appliances. This means sinks, showers, toilets and washing machines all draw water from the same source. All taps in this system provide potable (drinking) water since they connect directly to the mains supply.
How it works:
The system requires a non-return check valve at taps to prevent contamination of drinking water through back flow. Water pressure comes directly from the mains supply, providing consistent flow to all outlets.
Advantages of direct systems:
- Simple installation process
- Lower overall cost
- No large water storage cistern needed in the loft space
- Drinking water available from all taps throughout the property
- Reduced pipework in the loft area (minimising freezing risk)
Disadvantages of direct systems:
- Water pressure drops during peak usage times
- Higher failure rate of fittings due to mains pressure
- No backup water supply if mains supply fails
Indirect cold water supply system
The indirect system splits the incoming mains water in two directions. One branch feeds directly to the kitchen tap, whilst the other fills a storage tank (cistern) in the loft space. Individual appliances draw water from this cistern rather than directly from the mains.
How it works:
Only the kitchen tap connects directly to the mains supply, making it the sole source of drinking water and the only high-pressure outlet in the system. All other appliances receive water from the elevated storage tank, which provides constant pressure through gravity feed.
Storage tank specifications:
Storage Tank Requirements for Typical Installation
A typical four-bedroom house requires a storage tank with 340 litres capacity. When full, these tanks become extremely heavy, requiring support spread across at least four joists.
Essential components include:
- Ball/float valve to control water level
- Overflow fitting to prevent water damage
- Stop valve for maintenance access
- Insulated cover and pipework
The tank and associated pipework need insulation to prevent freezing during cold weather. Proper structural support is critical - never install a large storage tank without adequate joist support.
Advantages of indirect systems:
- Reserve water supply maintained if mains supply fails
- Consistent pressure on all taps (except kitchen tap)
- Overflow fitting prevents water damage from overfilling
Disadvantages of indirect systems:
- Higher installation cost due to additional pipework and fittings
- Large water storage tank required in loft space
- Drinking water only available at kitchen sink
System selection considerations
The choice between direct and indirect systems depends on several factors:
Direct systems suit properties where:
- Installation costs must remain low
- Loft space is limited
- Drinking water access from multiple points is desired
- Mains water pressure is reliable
Indirect systems work better where:
- Backup water supply is essential
- Consistent water pressure throughout the property is required
- Mains water pressure varies significantly
Key Points to Remember:
- Direct systems provide drinking water from all taps but rely entirely on mains pressure and supply
- Indirect systems offer backup water storage and consistent pressure but limit drinking water to the kitchen tap only
- Stop valves and drain valves are essential components for system maintenance and emergency shutoff
- Storage tanks in indirect systems require proper support across at least four joists and full insulation
- Pipe fittings connect different sections of the system and come in various materials and configurations