Other services in building

Septic tank

A septic tank is a watertight, underground, single-storey sedimentation and digestion tank that treats the sewage of a household or small building where no public sewer exists. Solids settle at the bottom as sludge and are digested by anaerobic bacteria; the partly clarified liquid (effluent) flows out for further treatment in a soak pit.

Parts: inlet pipe with a T-baffle (dip pipe), settling chamber, sludge zone, scum zone, outlet T-pipe, vent pipe, access manhole with cover. Often two chambers are provided with a dividing wall (first chamber 2/3 of length).

  inlet    manhole        vent   outlet
    |        |             |       |
 ===v========v=============v=======v==== GL
 | T          scum layer       |   T   |
 |___|                         |___|   |
 |   liquid (effluent zone)    |       |
 |   sludge digestion zone  [] |       |
 |_____________________________|_______|
     chamber 1 (2/3)         chamber 2

Working: sewage enters, flow velocity drops; heavy solids settle, light fats float as scum; anaerobic bacteria reduce sludge volume (about 30-50%) producing gas that escapes through the vent. Clear effluent leaves via the outlet.

Design points (IS 2470 / Nepal practice): detention time about 24 hours; sewage 90-135 L/person/day; sludge allowance about 30 L/person/year with desludging interval 1-2 years; length : width = 2:1 to 4:1; width not less than 0.75 m; liquid depth 1.0-1.8 m; free board 0.3 m; walls of brick in cement mortar plastered inside with waterproofing; floor and cover of RCC.

Soak pit

A soak pit (soakaway) is a circular pit that receives effluent from the septic tank and lets it percolate into the surrounding soil.

Construction: circular, diameter 1.0-2.5 m (typically 1.5 m) and depth 1-3 m, lined with dry brick masonry with honeycomb openings; filled with brick bats/stone aggregates (coarse at the bottom, finer above); covered with RCC slab having a manhole; the inlet pipe enters near the top.

  from septic tank
        |      cover slab
   =====v======+====== GL
   |  honeycomb brick wall |
   |  ooo brick bats ooo   |
   |  ooo aggregate  ooo   |
   |_______________________|
        |   |  seepage -> soil

Conditions: soil must be permeable, water table well below the pit bottom, and the pit at a safe distance (about 15 m or more) from drinking-water sources and 3 m from building foundations. Where soil is impermeable, use a leach/drain field or an absorption trench instead.

Rainwater harvesting (RWH) is the collection and storage of rain falling on roofs or ground for later use, or for recharging groundwater, instead of letting it run off.

Reasons

• Water scarcity and falling groundwater levels, especially in urban areas like the Kathmandu valley.
• Poor or irregular piped water supply; reduces dependence on tankers and groundwater pumping.
• Reduces surface runoff, urban flooding and soil erosion.
• Rain water is soft and nearly free of salts; cheap and simple to collect.
• Saves cost of water and energy; helps groundwater recharge.

Methods

• Rooftop harvesting: roof water is led via gutters and down pipes through a first-flush device and filter to a storage tank for use.
• Surface runoff harvesting: collection in ponds or tanks.
• Groundwater recharge: through pits, trenches and wells.

Components of rooftop RWH

1. Catchment: the roof (RCC, tiles, GI sheet) that receives rain; clean and non-toxic surface.
2. Gutters: half-round channels at roof edge (GI, PVC, aluminium) with slope about 1 in 100 leading water to the down pipe; fitted with mesh to stop leaves.
3. Down-take (conveyance) pipes: PVC pipes (75-100 mm) taking water from gutters to storage.
4. First-flush device: diverts the first dirty rain (first 10-15 minutes or about 0.5-1 mm of rain) containing dust, bird droppings and leaves to waste.
5. Filter unit: layers of coarse sand, gravel and charcoal (or mesh/sand filter) to remove suspended matter.
6. Storage tank: underground or overhead tank (RCC, ferrocement, plastic) sized for demand and rainfall; with inlet, overflow, outlet, vent, and cleaning provision.
7. Recharge structure (optional): recharge pit, trench, or well for the overflow.
8. Disinfection / delivery: chlorination or UV before drinking use; pump and distribution.

   \   roof (catchment)   /
  ===+====================+===
     |gutter              |
     v                    |
   down pipe              |
     |                    |
 [first flush]--> waste   |
     |
 [ filter: gravel/sand/charcoal ]
     |
 [ storage tank ]--overflow--> recharge pit
     |
   pump -> use

Benefits

• Supplements water supply and reduces water bill.
• Raises the groundwater table and improves its quality (dilutes fluoride, salts).
• Reduces urban flooding and erosion.
• Easy, low-cost technology and can be used in any building; suitable for toilets, gardening, washing and, after treatment, drinking.

Design: volume = rainfall (m) x roof area (m^2) x runoff coefficient (0.8-0.9 for roofs).

Rainwater harvesting (RWH) is the collection and storage of rain falling on roofs or ground for later use, or for recharging groundwater, instead of letting it run off.

It is mainly done from rooftops: rain falls on the roof, is collected by gutters, passes through a first-flush device and a filter, and is stored in a tank or sent to recharge pits. - Water scarcity and falling groundwater levels, especially in urban areas like the Kathmandu valley.

Treatment of rainwater

Rain water is relatively pure but picks up dust, leaves, bird droppings and microbes from the roof and air. Treatment steps:

1. Screening: mesh at gutters and inlet removes leaves and large debris.
2. First-flush diversion: discards first 10-15 minutes of dirty rain.
3. Sedimentation: settling in a tank allows suspended particles to settle.
4. Filtration: a gravity filter with layers of coarse gravel (bottom), fine gravel, sand and charcoal (top) removes turbidity, odour and colour. Slow sand filter or ceramic candle filter can be used for drinking water.
5. Disinfection: chlorination (about 2-4 mg/L of bleaching powder dose, to leave 0.2-0.5 mg/L residual), boiling, UV, SODIS (solar disinfection), or ozone, to kill pathogens.
6. Storage care: closed, dark tank with a mosquito-proof vent and cleaned yearly.

 rain -> [mesh] -> [first flush] -> [sedimentation]
        -> [sand-gravel-charcoal filter] -> [disinfection]
        -> storage tank -> use

Electricity can cause shock, burns and fire, so every stage of electrification of a building must follow safety rules (Nepal Electricity Act / Rules, NBC 206, and IS 732).

Safety precautions

• Earthing: connect all metal parts of appliances and the DB to earth (earth pit with GI plate/pipe, resistance less than 5 ohm for buildings) to avoid shock.
• Protective devices: fuses, MCB, MCCB, and ELCB/RCD (30 mA) to cut supply on overload, short circuit and leakage; lightning arrester on the roof.
• Proper materials: use standard-quality wires, switches and fittings with correct current rating; use proper size of conductor (sizes by load).
• Switch only on live (phase) wire: switches and fuses on phase; neutral solid; use 3-pin plugs.
• Insulation and joints: all joints properly made and insulated; no bare wire; use junction boxes.
• Avoid overloading: do not connect many appliances to one socket; use separate circuits for heavy loads (AC, geyser).
• Safe location: keep wiring away from water pipes, gas lines and hot surfaces; sockets and switches out of reach of children and away from bathrooms (or waterproof type); sufficient height.
• During work: switch off the main supply before repair; use insulated tools, rubber gloves and mats, and "danger/men at work" notices; avoid working in wet conditions; qualified electricians only.
• Fire precautions: keep extinguishers (CO2/dry powder) nearby; never use water on electrical fire.
• Testing and maintenance: test insulation resistance (megger) and earth continuity after installation and periodically.

Wiring is the system of conductors, switches and fittings used to distribute electric power in a building. Wiring may be classified by the method of fixing.

1. Cleat wiring

PVC or VIR cables held in porcelain/wooden cleats on the wall. Cheap and temporary; used in construction sites and exhibitions. Poor appearance and unsafe.

2. Casing-capping wiring

Cables laid in grooves of wooden casing covered by capping. Cheap and old; fire risk and affected by moisture and termites; rarely used now.

3. Batten wiring

Cables run on teak wood battens, clipped on the wall. Looks neat and is cheap, but poor against moisture and fire; used in dry places.

4. Conduit wiring

Cables drawn inside PVC or GI pipes (conduits).

• Surface conduit: fixed on the wall surface; easy to repair, used in workshops.
• Concealed conduit: buried in plaster or slab; best appearance, safe against fire, moisture and mechanical damage. Most used in modern buildings but costly and difficult to alter.

5. Lead-sheathed (CTS/TRS) wiring

Cables with a tough rubber sheath or lead cover clipped directly. Resists moisture; used in damp areas; costly.

6. Others

Metal-sheathed cable, bus-duct/trunking (large buildings and industry), underground cable.

Comparison: concealed conduit is the safest and neatest, batten is cheapest, and conduit/trunking is used for most multistorey buildings.

Systems of distribution: tree (branch) system and ring/loop system are the two layouts; the ring system has better voltage and reliability.

Rainwater harvesting (RWH) is the collection and storage of rain falling on roofs or ground for later use, or for recharging groundwater, instead of letting it run off.

Components of rooftop RWH

1. Catchment: the roof (RCC, tiles, GI sheet) that receives rain; clean and non-toxic surface.
2. Gutters: half-round channels at roof edge (GI, PVC, aluminium) with slope about 1 in 100 leading water to the down pipe; fitted with mesh to stop leaves.
3. Down-take (conveyance) pipes: PVC pipes (75-100 mm) taking water from gutters to storage.
4. First-flush device: diverts the first dirty rain (first 10-15 minutes or about 0.5-1 mm of rain) containing dust, bird droppings and leaves to waste.
5. Filter unit: layers of coarse sand, gravel and charcoal (or mesh/sand filter) to remove suspended matter.
6. Storage tank: underground or overhead tank (RCC, ferrocement, plastic) sized for demand and rainfall; with inlet, overflow, outlet, vent, and cleaning provision.
7. Recharge structure (optional): recharge pit, trench, or well for the overflow.
8. Disinfection / delivery: chlorination or UV before drinking use; pump and distribution.

   \   roof (catchment)   /
  ===+====================+===
     |gutter              |
     v                    |
   down pipe              |
     |                    |
 [first flush]--> waste   |
     |
 [ filter: gravel/sand/charcoal ]
     |
 [ storage tank ]--overflow--> recharge pit
     |
   pump -> use

Sizing: storage volume = rainfall (m) x catchment area (m^2) x runoff coefficient (about 0.8-0.9 for roofs). Example: 100 m^2 roof, 1.5 m rain, 0.85 gives 127.5 m^3 per year.

Fire protection in a building means all measures that prevent fire, limit its spread, protect occupants, and extinguish it. It has passive and active parts (NBC 109 and NBC 205 for fire safety).

Passive protection (built into the structure)

• Non-combustible, fire-resistant materials and structural members of proper fire rating (concrete cover, steel encasement).
• Compartmentation by fire walls, fire doors and fire stops.
• Means of escape: enough exits, fire-resistant protected staircases, exit signs, emergency lights; travel distance limits.
• Open spaces around the building and access for fire engines.
• Smoke ventilation and enclosed shafts.

Active protection

• Detection and alarm: smoke/heat detectors, call points, alarm panels.
• Extinguishing: portable extinguishers, hose reels, hydrants, wet/dry risers, automatic sprinklers, static water tank and pumps, CO2 or foam systems.
• Fire lifts and pressurised stairs in tall buildings.

Fire prevention

Safe electrical wiring, safe storage of flammable materials, no-smoking areas and regular drills and inspection.

 Prevent -> Detect -> Alarm -> Escape -> Extinguish -> Contain

Water supply in buildings brings treated water from the public main (or a well/tank) to taps and fixtures at adequate quantity and pressure.

Systems of distribution

1. Direct (up-feed) system: water comes straight from the main to fixtures; used where mains pressure is sufficient and supply is continuous. Cheap, but no storage and pressure variation.
2. Indirect (down-feed) system: water is first stored in an underground sump, pumped to an overhead tank on the roof, and distributed by gravity. Used in multistorey buildings and where supply is intermittent (usual in Nepal).
3. Combined system: a mix of both; ground-floor taps directly, upper floors via tank.
4. Hydropneumatic system: pressure vessel and pump, no overhead tank.

 Main -> [sump] -> pump -> [overhead tank] -> down pipes
                                   |-> floors / fixtures

Design

1. Demand: 135 L/person/day for residences (NBC/IS 1172); offices 45 L; schools 45 L; hospitals 340 L per bed (about).
2. Storage: overhead tank about 1/3 of daily demand, underground sump 1/2 - 1 day demand.
3. Pipes: sizes chosen from demand and velocity (0.9-2.4 m/s), pressure loss computed by Hazen-Williams equation; minimum residual head at the highest tap about 3-5 m.
4. Layout: short, straight runs, valves on branches, pipes (GI/HDPE/PVC/CPVC) in ducts, not under foundations; provision of air release and drain valves.

Building services

Building services are the installations that make a building functional, safe and comfortable apart from its structure. They include: water supply, drainage and sanitation, electrical supply and lighting, fire protection, ventilation and air conditioning, lifts and escalators, gas supply, telecom/IT, and waste disposal. They are planned along with architectural and structural design so that shafts, ducts and spaces are provided early.

Septic tank

A septic tank is a watertight, underground, single-storey sedimentation and digestion tank that treats the sewage of a household or small building where no public sewer exists. Solids settle at the bottom as sludge and are digested by anaerobic bacteria; the partly clarified liquid (effluent) flows out for further treatment in a soak pit.

Parts: inlet pipe with a T-baffle (dip pipe), settling chamber, sludge zone, scum zone, outlet T-pipe, vent pipe, access manhole with cover. Often two chambers are provided with a dividing wall (first chamber 2/3 of length).

  inlet    manhole        vent   outlet
    |        |             |       |
 ===v========v=============v=======v==== GL
 | T          scum layer       |   T   |
 |___|                         |___|   |
 |   liquid (effluent zone)    |       |
 |   sludge digestion zone  [] |       |
 |_____________________________|_______|
     chamber 1 (2/3)         chamber 2

Working: sewage enters, flow velocity drops; heavy solids settle, light fats float as scum; anaerobic bacteria reduce sludge volume (about 30-50%) producing gas that escapes through the vent. Clear effluent leaves via the outlet.

Design points (IS 2470 / Nepal practice): detention time about 24 hours; sewage 90-135 L/person/day; sludge allowance about 30 L/person/year with desludging interval 1-2 years; length : width = 2:1 to 4:1; width not less than 0.75 m; liquid depth 1.0-1.8 m; free board 0.3 m; walls of brick in cement mortar plastered inside with waterproofing; floor and cover of RCC.

Soak pit

A soak pit (soakaway) is a circular pit that receives effluent from the septic tank and lets it percolate into the surrounding soil.

Construction: circular, diameter 1.0-2.5 m (typically 1.5 m) and depth 1-3 m, lined with dry brick masonry with honeycomb openings; filled with brick bats/stone aggregates (coarse at the bottom, finer above); covered with RCC slab having a manhole; the inlet pipe enters near the top.

  from septic tank
        |      cover slab
   =====v======+====== GL
   |  honeycomb brick wall |
   |  ooo brick bats ooo   |
   |  ooo aggregate  ooo   |
   |_______________________|
        |   |  seepage -> soil

Conditions: soil must be permeable, water table well below the pit bottom, and the pit at a safe distance (about 15 m or more) from drinking-water sources and 3 m from building foundations. Where soil is impermeable, use a leach/drain field or an absorption trench instead.

• Supplements water supply, reduces dependency on piped supply and tanker water, and cuts water bills.
• Recharges groundwater and raises the water table.
• Reduces storm runoff, urban flooding and soil erosion.
• Rain water is soft and low in salts, good for washing and gardening, and (treated) for drinking.
• Simple, cheap, and easy to maintain; can be used anywhere.

Rainwater harvesting

Rainwater harvesting (RWH) is the collection and storage of rain falling on roofs or ground for later use, or for recharging groundwater, instead of letting it run off.

Reasons

• Water scarcity and falling groundwater levels, especially in urban areas like the Kathmandu valley.
• Poor or irregular piped water supply; reduces dependence on tankers and groundwater pumping.
• Reduces surface runoff, urban flooding and soil erosion.
• Rain water is soft and nearly free of salts; cheap and simple to collect.
• Saves cost of water and energy; helps groundwater recharge.

Basic components

Catchment (roof), gutters, down pipes, first-flush device, filter, storage tank (and recharge pit for overflow).

Components of the rooftop system

1. Catchment: the roof (RCC, tiles, GI sheet) that receives rain; clean and non-toxic surface.
2. Gutters: half-round channels at roof edge (GI, PVC, aluminium) with slope about 1 in 100 leading water to the down pipe; fitted with mesh to stop leaves.
3. Down-take (conveyance) pipes: PVC pipes (75-100 mm) taking water from gutters to storage.
4. First-flush device: diverts the first dirty rain (first 10-15 minutes or about 0.5-1 mm of rain) containing dust, bird droppings and leaves to waste.
5. Filter unit: layers of coarse sand, gravel and charcoal (or mesh/sand filter) to remove suspended matter.
6. Storage tank: underground or overhead tank (RCC, ferrocement, plastic) sized for demand and rainfall; with inlet, overflow, outlet, vent, and cleaning provision.
7. Recharge structure (optional): recharge pit, trench, or well for the overflow.
8. Disinfection / delivery: chlorination or UV before drinking use; pump and distribution.

   \   roof (catchment)   /
  ===+====================+===
     |gutter              |
     v                    |
   down pipe              |
     |                    |
 [first flush]--> waste   |
     |
 [ filter: gravel/sand/charcoal ]
     |
 [ storage tank ]--overflow--> recharge pit
     |
   pump -> use

Why necessary

• Water scarcity and falling groundwater levels, especially in urban areas like the Kathmandu valley.
• Poor or irregular piped water supply; reduces dependence on tankers and groundwater pumping.
• Reduces surface runoff, urban flooding and soil erosion.
• Rain water is soft and nearly free of salts; cheap and simple to collect.
• Saves cost of water and energy; helps groundwater recharge.

Method: rooftop harvesting with storage

Rain falling on the roof is collected and stored for use. Steps:

1. Roof area (catchment) should be clean; gutters fixed with slope of about 1:100 at the eaves.
2. Water flows through down pipes (75-100 mm).
3. First flush diverter discards the initial dirty water.
4. Water passes through a filter (gravel, sand, charcoal).
5. Clean water is stored in a tank (underground or overhead, RCC/plastic/ferrocement) with overflow to a recharge pit.
6. Disinfection (chlorine) if used for drinking.

  roof -> gutter -> down pipe -> first flush -> filter
        -> storage tank -> use ; overflow -> recharge pit

Storage capacity = rainfall x roof area x runoff coefficient (0.8-0.9).

Other method (groundwater recharge): filtered roof runoff is led to a recharge pit or trench (1-2 m wide, 2-3 m deep) filled with boulders, gravel and sand, or to a recharge well so that it soaks into the aquifer.

1. Rooftop rainwater harvesting (for storage)

Rain from roofs is collected through gutters and pipes and stored in tanks for use (domestic, gardening). Suited to houses and apartments.

2. Surface runoff harvesting

Rain flowing on the ground (roads, open land, courtyards) is collected in ponds, tanks, or reservoirs. Common in rural Nepal and in towns where open areas exist.

3. Groundwater recharge

Rain is led to the ground to raise water table, by:

• Recharge pits and trenches filled with boulders, gravel and sand.
• Recharge (dug or bore) wells through which filtered water goes to aquifers.
• Percolation ponds and gravel-filled recharge shafts.
• Permeable pavement and kerb-side recharge.

4. Direct use vs recharge

Storage tanks give immediate supply; recharge methods are used where space is limited or the rainfall is seasonal and storage is uneconomical.

Roof-top storage and recharge pits are the two most common methods for buildings.

Features of a building for fire safety (NBC 109 / NBC 205 "Fire Safety")

1. Fire-resisting materials and structure: structural members (columns, beams, floors, walls) of non-combustible materials with specified fire resistance rating (1-4 h), e.g., RCC with sufficient cover.
2. Compartmentation: division of the building by fire-resisting walls and floors to limit spread; fire doors on openings.
3. Means of escape: enough exits, protected corridors and stairs (fire-resistant, smoke-free), travel distance within limits, exit signs and emergency lighting, minimum two exits for multi-storey buildings.
4. Fire separation and setbacks: open spaces around building for fire vehicle access and to avoid spread to neighbours.
5. Fire detection and alarm: smoke or heat detectors, manual call points, and alarms.
6. Fire fighting installation: extinguishers, hose reels, wet or dry riser, hydrants, sprinklers, and an underground/overhead static fire tank.
7. Ventilation and smoke control: openings or exhaust to remove smoke; avoid vertical shafts spreading fire.
8. Safe electrical wiring and storage of flammables and a refuge area or fire lift in tall buildings.
9. Access for fire engines: road width, turning space, and hydrant connections.

First flush

The first flush is the first portion of rainfall after a dry spell which washes the roof and carries dust, bird droppings, leaves and pollutants. A first-flush diverter discards this water.

How it is used: a vertical pipe (about 100 mm) with a ball float valve or a diverter chamber is fitted on the downpipe before the filter. The first 10-15 minutes of rain (about 0.5-1 L per m^2 of roof) fills it; once full, the float closes the diversion and clean water flows on to the filter and tank. The collected dirty water is drained through a small slow-release hole. This keeps the stored water cleaner and reduces filter clogging.

   from roof
      |
      +---> to filter/tank (after chamber full)
      |
   [ chamber + ball float ]
      |
   small drain (dirty water out)

Fire spreads by conduction, convection and radiation, and through openings. The factors to consider to limit it are:

1. Choice of materials: use non-combustible and fire-resistant materials (brick, concrete, stone, fire-rated boards) for walls, floors, roofs and finishes; avoid highly combustible linings and furnishings.
2. Compartmentation: subdivide the building into fire compartments with fire walls and floors of rated resistance, so that fire stays in the room of origin.
3. Protection of openings: fire doors, fire shutters, and fire-rated glazing; sealing of pipe and duct penetrations with fire stops.
4. Vertical spread control: enclosed fire-resisting stairs, lift shafts and service ducts; spandrel beams or projections between windows to stop flames climbing the facade; fire dampers in ducts.
5. Separation between buildings: adequate distance and fire-resisting external walls to stop radiation and ignition of neighbours.
6. Fire resistance of structure: adequate concrete cover to rebars, protection of steel by encasement, plaster or intumescent paint.
7. Surface spread of flame: use finishes with low flame-spread rating on walls and ceilings.
8. Smoke control and ventilation: vents, smoke curtains and pressurised stairs.
9. Detection and fighting systems: early detection, sprinklers and hydrants to put out fire quickly.
10. Good housekeeping and wiring: proper electrical installation, and safe storage of flammable materials.

Fire detection systems

Early detection allows escape and quick action. Types of detectors:

1. Heat detectors: fixed-temperature (fusible link, bimetallic) or rate-of-rise types; respond to temperature increase; used in kitchens, boiler rooms.
2. Smoke detectors: ionisation type (good for flaming fires) and optical/photoelectric type (good for smouldering fires); used in rooms, corridors, offices.
3. Flame detectors: infrared or ultraviolet sensors for hazardous areas.
4. Gas detectors: detect combustible gases and CO.
5. Manual call points: break-glass push buttons.
6. All connect to a fire alarm panel with bells/sirens and indicator zones.

Fire extinguishing systems

1. Portable extinguishers: water (Class A), foam (A, B), CO2 (B, C, electrical), dry chemical powder (A, B, C), wet chemical (kitchen oils).
2. Hose reels and hydrants: pipes with hoses on each floor and outside hydrants.
3. Wet riser / dry riser: vertical pipe to supply water to floors in tall buildings (wet riser always charged, dry riser charged by fire brigade).
4. Automatic sprinkler system: pipe network with heat-sensitive bulbs (about 68 degrees C glass bulb) that burst and spray water over the fire.
5. Gaseous / foam systems: CO2, inert gas, or foam flooding for server rooms, stores and oil hazards.
6. Water storage: underground static tank and terrace tank with pumps (main, jockey, standby).

 Terrace tank
    |
  riser ---[hose reel] floor 3
    |-----[hose reel] floor 2
    |-----[hose reel] floor 1
  pump <- underground tank

A fire extinguisher is a portable device that discharges an agent (water, foam, gas or powder) to put out small fires in the early stage. It is a steel cylinder with a safety pin, handle, nozzle/hose and pressure gauge.

Classes of fire and suitable extinguishers

Operation (PASS): Pull the pin, Aim at the base of the fire, Squeeze the handle, Sweep side to side.

Placement: near exits and corridors, about 1 m above the floor, one for about every 200-250 m^2 of floor area, easy to see and reach, with color codes (red body; water red, foam cream, CO2 black, dry powder blue). Inspect regularly and refill after use.

Electrification system

Electrification of a building means bringing the electric supply from the utility line and distributing it safely to all lights, fans, sockets and appliances.

1. Service connection from the pole/transformer through service cable to the energy meter (with main fuse/cut-out).
2. Main switch and main distribution board (MDB), with MCCB/MCB and ELCB.
3. Sub-circuits: separate circuits for lighting (5 A, about 10 points per circuit) and power (15 A sockets), and heavy loads (AC, geyser, motor).
4. Wiring by conduit (concealed) with switches, sockets, fittings and earthing of the system.

 Pole -> meter -> main switch -> MDB -> circuits -> loads
                       earth pit

Protection from fire due to electricity

Electrical fires are caused by short circuit, overload, loose connections and poor insulation. Protective measures:

• Correct size of conductor and fuse/MCB rating; do not overload.
• Quality wires, joints insulated and enclosed in junction boxes; conduit to hold sparks.
• MCB/MCCB for overcurrent, ELCB/RCD for earth leakage; proper earthing; lightning arrester.
• Keep wires away from flammable materials and heat; maintain clearances.
• Regular inspection and insulation testing.
• Use CO2 or dry powder extinguishers (not water) for electrical fires, and switch off the mains first.

The fundamental requirements of good electrical wiring are:

1. Safety: to persons and property - well-insulated conductors, protection by fuse/MCB/ELCB, proper earthing.
2. Adequate capacity: conductor size is sufficient for the load current, with a margin for future increase; voltage drop kept within 3-5%.
3. Durability: quality material that resists moisture, heat and mechanical damage for long life.
4. Economy: cost-effective in material and labour, short runs.
5. Accessibility: switches, boards and joints reachable for operation and repair.
6. Appearance: neat and concealed where possible, not spoiling the interior.
7. Flexibility and extension: easy to add points later.
8. Reliability: separate circuits so a fault does not stop the whole supply.
9. Compliance with the electricity rules and standards (IS 732, NBC 206).

General principles of electrical services

• Safety: protect people and property from shock and fire (earthing, fuses, MCB, RCD/ELCB).
• Adequacy: the number of points, capacity of wires and loads must be enough for present and future use.
• Economy and simple design: short runs, balanced loads on phases, minimum voltage drop (not more than 3-5%).
• Reliability and continuity: separate circuits for lighting (5 A) and power (15 A); a fault on one circuit should not stop others.
• Accessibility: distribution board at an accessible central location; switches at about 1.2-1.4 m height.
• Standards: follow the Nepal Electricity rules and standard (NBC / IS 732 / IEC); use ISI/NS marked materials.
• Appearance and flexibility: concealed wiring where possible; provision for extension; good lighting levels.

Wiring systems

1. Cleat wiring

PVC or VIR cables held in porcelain/wooden cleats on the wall. Cheap and temporary; used in construction sites and exhibitions. Poor appearance and unsafe.

2. Casing-capping wiring

Cables laid in grooves of wooden casing covered by capping. Cheap and old; fire risk and affected by moisture and termites; rarely used now.

3. Batten wiring

Cables run on teak wood battens, clipped on the wall. Looks neat and is cheap, but poor against moisture and fire; used in dry places.

4. Conduit wiring

Cables drawn inside PVC or GI pipes (conduits).

• Surface conduit: fixed on the wall surface; easy to repair, used in workshops.
• Concealed conduit: buried in plaster or slab; best appearance, safe against fire, moisture and mechanical damage. Most used in modern buildings but costly and difficult to alter.

5. Lead-sheathed (CTS/TRS) wiring

Cables with a tough rubber sheath or lead cover clipped directly. Resists moisture; used in damp areas; costly.

6. Others

Metal-sheathed cable, bus-duct/trunking (large buildings and industry), underground cable.

Comparison: concealed conduit is the safest and neatest, batten is cheapest, and conduit/trunking is used for most multistorey buildings.

Systems of distribution: tree (branch) system and ring/loop system are the two layouts; the ring system has better voltage and reliability.

Safety precautions in using electricity and appliances

• Earthing: connect all metal parts of appliances and the DB to earth (earth pit with GI plate/pipe, resistance less than 5 ohm for buildings) to avoid shock.
• Protective devices: fuses, MCB, MCCB, and ELCB/RCD (30 mA) to cut supply on overload, short circuit and leakage; lightning arrester on the roof.
• Proper materials: use standard-quality wires, switches and fittings with correct current rating; use proper size of conductor (sizes by load).
• Switch only on live (phase) wire: switches and fuses on phase; neutral solid; use 3-pin plugs.
• Insulation and joints: all joints properly made and insulated; no bare wire; use junction boxes.
• Avoid overloading: do not connect many appliances to one socket; use separate circuits for heavy loads (AC, geyser).
• Safe location: keep wiring away from water pipes, gas lines and hot surfaces; sockets and switches out of reach of children and away from bathrooms (or waterproof type); sufficient height.
• During work: switch off the main supply before repair; use insulated tools, rubber gloves and mats, and "danger/men at work" notices; avoid working in wet conditions; qualified electricians only.
• Fire precautions: keep extinguishers (CO2/dry powder) nearby; never use water on electrical fire.
• Testing and maintenance: test insulation resistance (megger) and earth continuity after installation and periodically.

Electrical services in a building supply power for lighting, ventilation, appliances, communication and lifts. The general principles are:

• Safety: protect people and property from shock and fire (earthing, fuses, MCB, RCD/ELCB).
• Adequacy: the number of points, capacity of wires and loads must be enough for present and future use.
• Economy and simple design: short runs, balanced loads on phases, minimum voltage drop (not more than 3-5%).
• Reliability and continuity: separate circuits for lighting (5 A) and power (15 A); a fault on one circuit should not stop others.
• Accessibility: distribution board at an accessible central location; switches at about 1.2-1.4 m height.
• Standards: follow the Nepal Electricity rules and standard (NBC / IS 732 / IEC); use ISI/NS marked materials.
• Appearance and flexibility: concealed wiring where possible; provision for extension; good lighting levels.

Principles for laying out the water supply system in a building:

1. Adequate quantity and pressure at every fixture (min. residual head about 3-5 m); size pipes for peak demand.
2. Short, direct pipes with few bends and fittings to reduce friction loss and cost.
3. Storage: sump and overhead tank sized for demand; the tank at a height giving enough head to the top floor.
4. Valves: gate valve at each branch and fixtures, so parts can be isolated; air valves at high points and drain valves at low points.
5. Avoid contamination: keep water pipes separate from drains, never lay in contact with sewers, tank covered; pipes at least 0.5 m above sewer if crossing.
6. Protection: pipes in ducts or chases, lagged in cold places, not embedded under foundations or in columns; expansion allowed for.
7. Accessibility for repair; joints exposed or in inspection ducts.
8. Material: non-toxic, durable pipes (GI, HDPE, PVC, CPVC).
9. Grouping of fixtures around vertical shafts (kitchen and toilets stacked) for economy.
10. Hot and cold supply separate, with insulation on hot pipes.

Managing water supply and sanitation

1. Water supply: use a proper layout (sump, pump, overhead tank, distribution pipes) with adequate quantity (135 L/person/day) and pressure; clean the tanks regularly; fix leaks; use water-saving fixtures and recycle grey water; supplement by rain water harvesting.
2. Sanitation: separate soil (toilet) and waste (kitchen, bath) pipes, traps with water seal on every fixture, vent pipes to release gases, inspection chambers at bends/junctions with minimum slope (about 1 in 40 to 1 in 60 for house drains), and proper disposal by sewer or septic tank where there is no sewer.
3. Operation and maintenance: regular inspection, desludging of septic tank every 1-3 years, prevention of misuse (no solids, oils or chemicals), no mixing of storm water.

Septic tank and soak pit in sanitation

The septic tank receives toilet sewage, settles solids, digests sludge anaerobically and discharges clarified effluent to the soak pit, where it infiltrates into soil. Together they give on-site treatment and disposal in the absence of public sewers.

Septic tank

A septic tank is a watertight, underground, single-storey sedimentation and digestion tank that treats the sewage of a household or small building where no public sewer exists. Solids settle at the bottom as sludge and are digested by anaerobic bacteria; the partly clarified liquid (effluent) flows out for further treatment in a soak pit.

Parts: inlet pipe with a T-baffle (dip pipe), settling chamber, sludge zone, scum zone, outlet T-pipe, vent pipe, access manhole with cover. Often two chambers are provided with a dividing wall (first chamber 2/3 of length).

  inlet    manhole        vent   outlet
    |        |             |       |
 ===v========v=============v=======v==== GL
 | T          scum layer       |   T   |
 |___|                         |___|   |
 |   liquid (effluent zone)    |       |
 |   sludge digestion zone  [] |       |
 |_____________________________|_______|
     chamber 1 (2/3)         chamber 2

Working: sewage enters, flow velocity drops; heavy solids settle, light fats float as scum; anaerobic bacteria reduce sludge volume (about 30-50%) producing gas that escapes through the vent. Clear effluent leaves via the outlet.

Design points (IS 2470 / Nepal practice): detention time about 24 hours; sewage 90-135 L/person/day; sludge allowance about 30 L/person/year with desludging interval 1-2 years; length : width = 2:1 to 4:1; width not less than 0.75 m; liquid depth 1.0-1.8 m; free board 0.3 m; walls of brick in cement mortar plastered inside with waterproofing; floor and cover of RCC.

Soak pit

A soak pit (soakaway) is a circular pit that receives effluent from the septic tank and lets it percolate into the surrounding soil.

Construction: circular, diameter 1.0-2.5 m (typically 1.5 m) and depth 1-3 m, lined with dry brick masonry with honeycomb openings; filled with brick bats/stone aggregates (coarse at the bottom, finer above); covered with RCC slab having a manhole; the inlet pipe enters near the top.

  from septic tank
        |      cover slab
   =====v======+====== GL
   |  honeycomb brick wall |
   |  ooo brick bats ooo   |
   |  ooo aggregate  ooo   |
   |_______________________|
        |   |  seepage -> soil

Conditions: soil must be permeable, water table well below the pit bottom, and the pit at a safe distance (about 15 m or more) from drinking-water sources and 3 m from building foundations. Where soil is impermeable, use a leach/drain field or an absorption trench instead.

Domestic water supply system

It is the arrangement of pipes, tanks, pumps and fittings that brings water from the public main or a private source (well, spring) to the taps, WCs and appliances of a house, in sufficient quantity, pressure and quality. Typical parts: service connection with meter, underground sump, pump, overhead tank, distribution pipes with valves, and fixtures.

 Main -> meter -> sump -> pump -> roof tank
                                    |-> kitchen, bath, WC

Types: direct (up-feed), indirect (down-feed from a tank), and combined.

Types of drainage system

Drainage removes sewage and storm water from the building.

1. Combined system: one sewer carries both sewage and storm water. Cheap and one pipe, but large pipe, overload in rain and the treatment plant is overloaded.
2. Separate system: sewage in one pipe and storm water in another. More costly but pipes are smaller and treatment works get only sewage. Best for new areas.
3. Partially separate system: a small part of storm water (roof and courtyard) goes in the sewer, the rest in separate drains.

 Separate system
  house --soil pipe----> sewer -> treatment
  roof/yard --rain pipe-> storm drain -> river

Inside the building: single-stack system (one stack for soil and waste, vented), one-pipe system, two-pipe system (separate soil and waste stacks), and the modified one-pipe system. Fixtures have water seal traps, and inspection chambers are placed at bends and junctions. Outside: drains of vitrified clay, concrete or PVC laid to gradients of 1 in 40 to 1 in 100, connecting to the sewer or septic tank.

Domestic water supply system

It is the arrangement of pipes, valves, tanks and pumps that delivers water from the public main or source to taps and fixtures of a house in sufficient quantity, pressure and quality. Components: service pipe and meter, sump, pump, overhead tank (at least one-third of daily demand), distribution pipes, valves and fixtures. Demand is taken as 135 L/person/day.

 Main -> [sump] -> pump -> [roof tank] -> floors -> taps

Septic tank and soak pit system for a residential site

Where there is no public sewer, toilet sewage is treated on site by a septic tank, and the effluent goes to a soak pit.

Septic tank

A septic tank is a watertight, underground, single-storey sedimentation and digestion tank that treats the sewage of a household or small building where no public sewer exists. Solids settle at the bottom as sludge and are digested by anaerobic bacteria; the partly clarified liquid (effluent) flows out for further treatment in a soak pit.

Parts: inlet pipe with a T-baffle (dip pipe), settling chamber, sludge zone, scum zone, outlet T-pipe, vent pipe, access manhole with cover. Often two chambers are provided with a dividing wall (first chamber 2/3 of length).

  inlet    manhole        vent   outlet
    |        |             |       |
 ===v========v=============v=======v==== GL
 | T          scum layer       |   T   |
 |___|                         |___|   |
 |   liquid (effluent zone)    |       |
 |   sludge digestion zone  [] |       |
 |_____________________________|_______|
     chamber 1 (2/3)         chamber 2

Working: sewage enters, flow velocity drops; heavy solids settle, light fats float as scum; anaerobic bacteria reduce sludge volume (about 30-50%) producing gas that escapes through the vent. Clear effluent leaves via the outlet.

Design points (IS 2470 / Nepal practice): detention time about 24 hours; sewage 90-135 L/person/day; sludge allowance about 30 L/person/year with desludging interval 1-2 years; length : width = 2:1 to 4:1; width not less than 0.75 m; liquid depth 1.0-1.8 m; free board 0.3 m; walls of brick in cement mortar plastered inside with waterproofing; floor and cover of RCC.

Soak pit

A soak pit (soakaway) is a circular pit that receives effluent from the septic tank and lets it percolate into the surrounding soil.

Construction: circular, diameter 1.0-2.5 m (typically 1.5 m) and depth 1-3 m, lined with dry brick masonry with honeycomb openings; filled with brick bats/stone aggregates (coarse at the bottom, finer above); covered with RCC slab having a manhole; the inlet pipe enters near the top.

  from septic tank
        |      cover slab
   =====v======+====== GL
   |  honeycomb brick wall |
   |  ooo brick bats ooo   |
   |  ooo aggregate  ooo   |
   |_______________________|
        |   |  seepage -> soil

Conditions: soil must be permeable, water table well below the pit bottom, and the pit at a safe distance (about 15 m or more) from drinking-water sources and 3 m from building foundations. Where soil is impermeable, use a leach/drain field or an absorption trench instead.

 WC/bath -> inspection chamber -> septic tank -> soak pit