Potable Water Supply to Buildings – Study Notes (October 2024)

Water Sources and Abstraction

• Abstraction is the sourcing of the raw water that is treated before drinking.

• Three principal sources of raw water:

  • Surface water sources, i.e. rivers and large lakes

  • Boreholes into aquifers (water-bearing strata, groundwater)

  • Roofs, paved areas and shallow wells (rainwater collection non-potable in most urban contexts)

• A fourth possibility is desalination of seawater, but this is energy intensive and expensive; wastewater can be purified and recycled as a last resort.

• Impounding reservoir example: Inniscarra Dam, River Lee, Co. Cork (E.S.B.)

• Water Source percentages (as described):

  • Surface water can be sourced from local lakes, rivers, streams (80%) and natural springs (~7%)

  • Wells or boreholes into aquifers (water-bearing strata) (~11%)

  • Rooftops, paved areas (rainwater collection) (~2%)

• Lough Corrib is noted as a natural reservoir for Galway.

• Surface water sources are typically high above sea level to enable gravity flow through the treatment and distribution system where possible.

• Manmade reservoirs can be contained within clay-lined earth embankments or formed by flooding natural valleys (valleys may also be used for hydroelectricity via a dam).

• Shannon–Dublin Pipeline is a major water supply project for the Eastern and Midlands Region; key cross-sections include large-diameter mains and treatment/storage facilities (e.g. 2,000 mm and 1,700 mm lines at various points).

• A typical note: Water supply infrastructure operates with gravity where possible, aided by pumping and storage towers close to demand centers.

Water Treatment

• Depending on source water quality, different treatment regimes are designed to bring water up to potable standards; monitoring is continuous in line with EU Directives and Irish legislation (e.g., EU Drinking Water Regulations).

• Typical water quality parameters achieved in County Galway are accessible via local authority resources.

• The treatment process commonly aims to produce potable water that is colorless, clear, odourless, and pleasant to taste.

The Seven-Stage Water Treatment Process (as described in the lecture)

• Stage 1: Intake – Water is sourced from surface supplies (lakes/rivers) or underground sources (wells).

• Stage 2: Screening – Water passes through a fine mesh to remove debris (twigs, plants, etc.).

• Stage 3: Settling – Water moves into large settling/sedimentation tanks. Alum (Aluminum potassium sulphate) is added to remove cloudiness/discolouration.

• Stage 4: Filtration – Water passes through filters (slow sand filters, rapid sand filters, micro-strainers, membrane filters such as RO). Slow sand filtration combines physical and biological action; rapid sand filtration is primarily physical.

• Stage 5: Disinfection – Chlorination and/or ozonation (O3) are used to kill pathogens. UV treatment is also used.

• Stage 6: Fluoridation – Fluoridation is practiced in the Republic of Ireland; the percentage of population receiving fluoridated water varies by region (see fluoridation map/table).

• Stage 7: Storage and Distribution – Treated water is stored before distribution through networks to consumers.

• Note: The Irish context includes regulatory references and Galway water quality indicators; fluoridation practice varies by jurisdiction.

• Some contaminants and quality parameters monitored include color, odour, taste, turbidity, pH, chlorine, fluoride, faecal coliforms, Cryptosporidium, aluminium, trihalomethanes (e.g. chloroform), iron, ammonium, nitrates/nitrites, heavy metals, and manganese.

Contaminants and Water Quality Parameters

• Common parameters and contaminants monitored:

  • Colour

  • Odour

  • Taste

  • Turbidity

  • pH (neutral)

  • Chlorine

  • Fluoride

  • Faecal coliforms

  • Cryptosporidium

  • Aluminium

  • Trihalomethanes (e.g., chloroform)

  • Iron

  • Ammonium

  • Nitrates

  • Nitrites

  • Heavy metals

  • Manganese

• Some pathogens have different susceptibilities to disinfection methods (e.g., Cryptosporidium not killed by chlorine; UV can be effective against a wide range of pathogens).

Water Purification and Impurities

• Purification aims to remove contaminants to produce water suitable for its intended use, typically potable water for human consumption.

• Impurities can be grouped as:

  • Settleable solids

  • Suspended solids

  • Dissolved salts

  • Microbial life: bacteria, viruses, Cryptosporidium, etc.

• Purpose-built treatment profiles limit inclusion of specific materials while delivering safe, palatable water.

Methods of Water Treatment (General Principles)

• Storage/settlement and clarification to remove particulates

• Filtration: slow sand filters, rapid sand filters, micro-strainers, membrane filters (including reverse osmosis)

• Disinfection: chlorine, ozonation, UV light, and other methods

• Some sources describe a seven-stage process (as above) and variations, depending on local requirements.

Filtration Details: Slow vs Rapid Sand Filters

• Slow sand filters:

  • Large basins (e.g., 100 m × 40 m) with a bed of gravel and ~600 mm sand depth; water depth ~1 m above the bed.

  • Filtration relies on a moving biological film (schmutzdecke) that forms on the sand, providing physical and biological purification.

  • Filtration is slow, and the rate decreases as the biofilm develops; periodic cleaning is required (charged by refilling from the bottom).

  • Advantages: very high-quality water with minimal further treatment; disadvantages: large footprint and slower processing.

  • Cleaning: compressed air back-wash.

• Rapid sand filters:

  • Primarily physical filtration with higher flow rates; may require chemical treatment in addition to filtration.

Disinfection Methods

• Chlorination: oxidising agent that kills bacteria by dosing (injection into water).

• Ozonation (O3): powerful sanitizer with higher cost and operation complexity.

• UV treatment: sun-derived UV rays germicidally in water; effective against many pathogens (e.g., E. coli, Salmonella, Legionella, Mycobacterium tuberculosis, Poliovirus, Hepatitis A, Cholera, Streptococcus, and even SARS-CoV-2); however, some organisms like Cryptosporidium are resistant to chlorine and may require UV or other methods.

• Combined or sequential use of methods is common to ensure robust disinfection.

Alternative Water Treatment Approaches

• Alternative treatment approaches may include rapid gravity granular activated carbon filters, ozone-based systems, and advanced oxidation/reaction processes.

• Various proprietary media (e.g., Calgon Carbon) and treatment trains may be employed for particular industrial or municipal water requirements.

• Waste/discharge from water treatment plants is governed by EU directives and Irish legislation.

Water Distribution Networks

• Distribution networks consist of high-volume, high-pressure pipelines that gradually reduce in size toward dwellings and facilities.

• Distribution relies on gravity feed, pumped feed, or gravity-induced feed via water towers near high-demand centers.

• Major distribution infrastructure includes integrated reservoirs, treatment plants, and transfer mains that connect to local networks.

Rural Water Supply and Group Water Schemes

• Rural areas outside town/city networks are supplied via group water schemes in Ireland (approximately 8% of supply).

• These schemes are community-based and typically supported by government grants; water supply is partly privatised.

• The sustainability of the funding model is questioned due to high costs and aging infrastructure.

• Irish Water (Uisce Éireann) has stated that it costs about €1.2 billion per year to operate the public water system, with about €1 billion funded by the Exchequer; infrastructure overhaul is needed.

Water Metering and Consumption Management

• Water meters measure the volume of water supplied; meters are typically installed in a meter box on public land and use Automated Meter Reading (AMR) technology.

• AMR enables drive-by reading, reducing the need for on-site meter reads and providing usage data to help manage consumption.

• Irish Water/Uisce Éireann began nationwide meter installation in August 2013; by 2017 the majority of households had a meter; there is no direct charge for meter installation.

• How metering helps: detection of leaks, better water management, and price transparency in some regions.

Leaks, Losses, and Water Use Efficiency

• An estimated 33% to 50% of treated water is lost due to leaks in distribution pipes.

• Typical water use: about 150 L per day is treated per user, of which around 90 L reaches the user (roughly 60% delivered).

• Metering and leak detection play a crucial role in reducing non-revenue water and improving system efficiency.

Domestic Water Supply Details and Hygiene (TGD G Hygiene)

• The Technical Guidance Document (TGD) Part G: Hygiene provides guidance on meeting Building Regulations through safe design and construction practices.

• Downloads required for study: TGD Part G, Hygiene, reprint July 2011 edition (pages 5, 6, 7, 8 are emphasized for study).

• Focus areas include the design and installation of bathrooms, kitchens, sanitary conveniences, and washing facilities within dwellings.

• The document also covers the relationship between building services and drinking water safety, with emphasis on preventing contamination and ensuring clean, safe supply.

Domestic Cold Water Supply Details (Ground Level) and Stop Cocks

• All mains distribution pipework is under pressure and can be shut off locally using a stop valve.

• The stop valve is typically located underneath the kitchen sink and provides an easy shut-off to a dwelling.

• Meter housing, frost protection, and maintenance access: diagrams show space for maintenance, valve placement, and insulation requirements.

• The external service pipe from the meter to the dwelling has a minimum cover of $600\ ext{mm}$; the cover must be maintained along the whole length of the pipe.

• Insulation to protect against freezing is required where pipes pass through floors in contact with the ground or through suspended floors.

• Drainage arrangements and frost protection are specified near the stop valve, meter, and service pipe to maintain reliability in cold conditions.

Insulation and Frost Protection (TGD G Hygiene Appendix)

• The underground service pipe from the external meter/stopcock to the dwelling must have a minimum cover of $600\ ext{mm}$.

• Where the pipe is near an external wall, it should be insulated with insulation impermeable to water vapour.

• Diagrams illustrate insulation strategies for cold water supply through floors (ground level and above) with appropriate venting, ducting, and moisture control.

• Minimum insulation thickness (Table 1, Appendix of TGD G) provides guidelines for protecting cold water pipes against freezing across various pipe diameters and materials. The table lists thickness values that depend on outside diameter, inside diameter, and the thermal conductivity λ (in W/m·K).

  • Example values from the table (illustrative):

  • Outside diameter $15\ ext{mm}$; λ = $0.020\ ext{W/m·K}$ yields a thickness around $23\ \text{mm}$ to $35\ \text{mm}$ depending on the exact condition; thicker insulation values appear for lower λ and larger diameters (up to around $113\ \text{mm}$ for certain λ values).

• Practical notes accompanying the table emphasize that some listed insulation thicknesses may be impractical; higher insulation thicknesses may require larger pipe sizes, materials with lower thermal conductivity, or alternative means of heat input to maintain frost protection.

• Appendix note: thickness values are provided to illustrate the relative scale of insulation required for frost protection and must be chosen in the context of design requirements and practicality.

Assignment, Coursework, and Study Hints

• Assignment tasks focus on constructing neat, annotated diagrams of cold water feed from a distribution pipe into a dwelling, including a water meter, and compliance with TGD G Hygiene (Part G) requirements (e.g., Diagram 1 and associated notes).

• The assessment emphasizes accurate representation of the external service pipe, meter, stop valves, and the frost-protection measures required by the Regulations.

Figures, Maps, and Notable Examples Mentioned

• Inniscarra Dam as a representative impounding reservoir (Co. Cork).

• Lough Corrib highlighted as a natural reservoir for Galway.

• Ballyshannon hydroelectric dam and flooded valley as examples of valley-dam hydro projects.

• Shannon–Dublin Pipeline illustrating major cross-regional water transfer and treatment infrastructure.

• Ballinrobe Water Towers as distribution infrastructure examples.

• Galway, Luimnagh, Terryland, Clonbur, Cross, Cong, Comamona, Maum, Oughterard, Gortmore, Rosmuck, Costelloe, Canoma, Shrule, Kilb respectively as map references in a regional context.

• Diagram references show service pipe details, insulation strategies, and maintenance access points for domestic water supply.

Exam and Study Resources

• Sample exam question: WATER SERVICES (a) Discuss the abstraction, processing and distribution of a municipal mains water supply by the Water Authority (Uisce Éireann). (12 marks)

• The slides emphasize that the content is exam-relevant and encourage practice with sample questions to aid exam readiness.

Additional Notes on Hygiene, Legislation, and Industry Context

• Irish building regulations and TGDs: Part G provides hygiene guidance for building design and construction to meet regulatory standards.

• The TGDs indicate compliance when works follow the guidance; alternative approaches are permissible if they meet the Regulations.

• The July 2011 reprint of TGD Part G (Hygiene) is used as a study reference; students are instructed to download and bring pages 5, 6, 7, and 8 to class as part of coursework.

• Public water services are subject to ongoing infrastructure upgrades and regulatory oversight, including metering, leakage management, and resource sustainability considerations.

Quick Reference: Key Quantities and Concepts in LaTeX

• Indoor CO2 levels recommended (ASHRAE): <1000\ \mathrm{ppm} in schools, <800\ \mathrm{ppm} in offices.

• Surface water contribution: $80\%$; springs: $7\%$; groundwater boreholes: $11\%$; rainwater collection: $2\%$.

• Leak losses in distribution: $0.33\leq f\leq 0.50$ of treated water lost; per-user treatment: $150\ \mathrm{L/day}$; water reaching user: $90\ \mathrm{L/day}$; delivery efficiency: $60\%$.

• Water mains covers: $600\ \mathrm{mm}$ minimum.

• Insulation thickness examples (Table 1): for outer diameter $15\ \mathrm{mm}$ and thermal conductivity $\lambda = 0.020\ \mathrm{W/(m\cdot K)}$, thicknesses around $23-35\ \mathrm{mm}$ (illustrative; table contains a range up to $113\ \mathrm{mm}$ depending on conditions).

• Pipeline diameters in major projects: $2{,}000\ \mathrm{mm}$ and $1{,}700\ \mathrm{mm}$ entries in large transfer mains.

• Water usage metrics are often presented as volumetric per capita values (e.g., liters per day) to assess efficiency and leakage.

Summary Takeaways

• Drinking water supply involves a complex chain from abstraction to distribution, with multiple source types, treatment steps, and disinfection strategies.

• Filtration and disinfection are the core technical methods to ensure water safety, with redundancy through multiple disinfection methods to address resistant pathogens.

• The distribution network and metering play critical roles in managing losses, leak detection, and cost recovery, while regulatory guidance like TGD G Hygiene shapes design and installation practices.

• Rural water schemes and urban networks require coordinated governance, investment, and sustainability planning to maintain reliable potable water supplies.

• Practical considerations in domestic installations include proper pipe routing, frost protection, insulation, and metering hardware, all guided by national regulations and standards.