Chpater 27 ESSENTIAL SERVICES IN BUILDINGS – Building Construction Materials and Techniques

27

ESSENTIAL SERVICES IN BUILDINGS

27.1 INTRODUCTION

Essential elements for the human beings to live in a house with a minimum comfort are water supply, drainage arrangements and electrical power supply.

Biologically, water is required for the human beings for the satisfactory performance of physiological organisms, as a circulatory fluid, as a carrier of nourishing food and for the removal of products of wastes. Man uses water for variety of purposes. At the domestic end, a minimum requirement of water is needed for drinking, cooking, bathing and cleaning. Hence, a certain amount of water per head per day needed is being recommended. Accordingly the water requirement has to be made.

Disposal of wastewater, that is, used water from kitchen, toilet, cleaning, etc., has to be separately dealt for hygienic conditions.

At present, electricity has become an essential commodity as it is being used in the house for variety of works.

These essential services in a building are dealt in this chapter.

27.2 PLUMBING SERVICES

Plumbing services is the entire system of piping, fixtures, applications, etc., for providing water supply or drainage to a building or premises. A plumbing water supply system consists of water supply and distribution with the use of pipes, control valves, pipe layout, storage tanks, etc. A plumbing drainage system consists of collection and disposal of wastewater with the use of water closets, urinals, traps, vents, anti-siphonage pipes, house drains, house sewers, etc.

27.2.1 Plumbing Terms

Following are the terms to which a civil engineer should be familiar in connection with plumbing services.

1. Plumbing or Plumbing System

It is a general term encompassing the entire design practice, material and fixtures used in the installation and maintenance of all main fixtures and other appurtenances used in connection with water supply systems and wastewater collection and disposal systems.

2. Available Head

It is the pressure water available from a water main at the ground floor level to the premises.

3. Water Main

It is a main water supply pipeline intended for general use and maintained by local authority.

4. Service Pipe

It is a pipe branching out of the water main which is used for feeding water from the main pipe to the building.

5. Storage Tank

It is a tank for storing water from the water main by means of a supply pipe.

6. Stop Cock or Tap

It is a control valve used for regulating the supply of water.

7. Stack

It is a general term used for any line of drainage particularly vertical lines.

8. Back-Siphonage

It is the flow back of used or polluted water from a plumbing fixture or vessel into a water supply pipe due to negative pressure.

9. Trap

It is a fitting provided with a water seal so that when placed in a drainage pipe it prevents the passage of foul air or gas.

10. Soil Pipe and Waste Pipe

Soil pipe is used for liquid wastes carrying human excreta, whereas waste pipe carries only the liquid waste.

11. Vent Pipe

It is a pipe to allow air to or from a drainage system so as to prevent the water seal of traps against siphonage and back pressure.

12. Flushing Storage Tank

It is provided to supply water to all flushing cistern through downtake pipes.

13. Supply Pipe

It is the pipe which extends from the stop cock to the entrance of the storage tank.

14. Distributing Pipe

It is the pipe connecting the storage tank to various sanitary fixtures, taps, etc., for purposes of distribution of water supply inside the building.

15. Sullage and Sewage

Sullage is the spent water from bathrooms, kitchens, washbasins, sinks, etc. This does not include foul discharge (i.e., human or animal excreta as from water closets, urinals, hospitals, stables, etc.). Sewage includes both the sullage as well as the foul discharge explained above.

16. Night Soil

Night soil is a composite of human excreta and urine.

17. Sewer

It is a closed drain intended to be used for carrying sewage (i.e., night soil and other water-borne wastes).

18. Drain

It is a channel or pipe which carries wastewater or water-borne wastes in a building draining system.

27.2.2 Principles of Plumbing Services in Buildings

The following factors are to be considered while designing plumbing services to buildings:

  1. All foul and waste matter should be removed as quickly as possible.
  2. All possible passage of gases, odour or vermin from pipes and sewers into the building should be prevented.
  3. All drainage pipes should be airtight, gas-tight and strong enough and durable to withstand the corrosive action of liquid wastes.
  4. All pipe joints (both water supply and drainage) should be leak-proof and strong and durable.
  5. The entire network of pipes should have ample means of cleaning and removing obstructions.
  6. Every care has to be taken to check and rectify all possible air-locks, siphonage, under deposits and obstructions.
27.3 WATER SUPPLY

In villages and in some towns where municipal water supply is not available, water is obtained from private wells. In such places, usually the water is pumped up to an elevated storage tank from where the distribution to the building is carried out.

In large towns and cities, municipal water, after due treatment, is available through street mains. If adequate pressure is available, the municipal water can be directly connected to an overhead tank. If the pressure is less, a sump may be provided to collect the water from the municipal supply lime. The capacity of the low-level tank (sump) should be adequate enough to hold water depending on the supply system of the municipal authorities.

Water is pumped from this sump at regular intervals to an overhead tank from where the water is distributed to various parts of the building. In addition to the overhead tank, provision may be made to collect the municipal water directly for drinking and cooking purposes at a convenient place (kitchen) in the building. The water in the overhead tank will take care of other demands.

The capacity of the overhead tank is based on the number of persons using it. It is usually of 200–500 l. If it is more than 5000 l, it is better to average it in a series of interconnected tanks such that they can be easily cleaned. The overhead tanks may be of brick, concrete or readymade PVC tanks. An inlet pipe, on outlet pipe and a drainpipe are connected to each tank.

The underground (or sump) and overhead tanks should be cleaned at regular intervals. They should also be disinfected after cleaning by using chemicals. In some cases separate flushing storage overhead tank is provided exclusively for flushing water closets, etc., as the quantity of water used for this purpose is large and be of low quality. For example, bore well water may be used separately for this purpose. Flushing storage tanks may have the capacities as given in Table 27.1.

Table 27.1 Flushing storage capacities

27.3.1 Design of Water Distribution System

Water distribution system needed for a conventional residential building depends on the following aspects:

  1. Estimation of water requirement
  2. Determination of pipe sizes
  3. Pipe layout principles

1. Estimation of Water Requirement

As per Indian code recommendation (IS: 1172–1983 and SP 57–1993) for residences, 135 l of water per head per day to be used for the design of water supply system. The details of the daily consumption is given Table 27.2.

Table 27.2 Domestic consumption of water

Source: IS: 1172–1983.

The daily consumption will vary depending on the activities in a building. For example, in a hospital with beds, the consumption may be of the order of 340 l per bed per day and for a day school, the consumption will be as low as 45 l per head per day.

2. Determination of Pipe Sizes

In general for a middle class house the average number of pipes needed shall be about 8 and pipes of minimum nominal size of 20 mm diameter are enough. For WCs which are directly connected to overhead tanks, a 25 mm diameter is adequate to get sufficient flow. Minimum recommended size of pipes for different purposes in a building is shown in Table 27.3.

Table 27.3 Recommended sizes of water supply pipes

A thumb rule to assess the size of pipes which can supply two or more branch pipes is as follows (Varghese, 2012):

  1. Up to 3 numbers of 10 mm branches can be supplied by a 12 mm pipe.
  2. Up to 3 numbers of 12 mm branches can be supplied by a 20 mm pipe.
  3. Up to 3 numbers of 20 mm branches can be supplied by a 25 mm pipe.

In order to control the output from overhead tanks, a stop valve or gate valve must be fixed in an accessible place. Apart from control this will help to stop the water supply during repairs.

For multi-storey buildings with many flats, a more complex arrangement of water distribution system should be planned.

3. Pipe Layout Principles

Following rules may be adopted in laying of water supply lines (Varghese, 2012):

  1. There should not be any cross connection and backflow. Backflow can be eliminated by ensuring the under mentioned conditions.
    1. Adequate air gap is to be provided between the inlet and final flood level in all places particularly washbasins.
    2. While connecting cistern to water closet, the inlet and float valve should be suitably fixed.
    3. Positive pressure at the outlet pipes should always be assured.
  2. Drainage pipes and water supply pipes should not be laid very close to each other. Especially drainage stoneware pipe which are liable to leak if damaged should not be laid above the water supply line. Further, water supply pipes should not be laid alongside of the pipes carrying foul water.
  3. Planning of the distribution line should be such that it is accessible for inspection, replacement and repairs. GI pipes should not be buried as they tend to corrode in contact with soils, but they can be laid on walls.
  4. All pipes including PVC pipes laid inside the building as concealed pipes should be tested for leakage.

27.3.2 Water Supply Fittings and Fixtures

Most of the fittings which are to be used for the water supply are standardised. Some of the fittings which are routinely used in residential water supply are discussed below.

1. Stop Valves

These are fixed in an accessible place for each outlet such as washbasins, water closets, etc., to control and facilitate repair.

2. Gate Valves

These operate as a gate in the pipe. It regulates the flow and when fully open, it offers no resistance to flow. These are used for closing the main pipes from tanks.

3. Ball or Float Valves

These are provided in storage tanks, flushing cistern, etc., to control the level of storage water. The supply is cut off automatically when the water reaches a particular designed level.

4. Bib Taps or Bib Cocks

This is the conventional type of fittings used in washbasins.

5. Pillar Taps

It is the outlet provided from a vertical inlet and horizontal outlet in washbasins in kitchens, lavatories, etc.

6. Self-Closing Taps

They remain open as long as the valve is pressed down and closes when the pressure is released. Such taps are provided in railway stations, hotels, etc.

7. Magnetic Taps

These taps operate as soon as the hand is placed below the tap and closes automatically as soon as the hand is removed. This is a very hygienic tap as one need not to touch the tap to operate. Such taps are provided in airport, hotels and hospitals.

27.3.3 Materials of Water Pipes

Two main types of pipes are Galvanised-iron (GI) pipes and unplasticised Poly-vinyl chloride (UPVC) pipes.

If the quality of water running through the pipe is good, and the pipes are buried GI pipes are excellent. These pipes are available in three grades, viz., A, B and C. Class C is the pipe meant for heavy duty and is cosliest of all. Grade B pipes are generally used for water supply in buildings. In order to identify the type of pipes different colours are used, viz., yellow for grade A, blue for grade B and red for grade C.

UPVC pipes are now-a-days preferred for water supply in buildings. They do not function well when exposed to sunlight. Further the coefficient of expansion of UPVC pipes is about eight times greater than that of GI pipes. UPVC pipes require supports at closer intervals.

27.4 DRAINAGE OF WASTEWATER AND SEWAGE

Wastewaters coming from kitchen sink, washbasins and urinals are not containing any solid matter. But sewage a solid material has to be treated such that it also could be converted as a wastewater.

27.4.1 Need for Treatment of Sewage

Nearly 75% of the water supplied returns back in the form of wastewater. As there is a need for water supply system, there is an equal necessity to dispose the wastewater. The night-soil and urinary content of domestic sewage (originating from residential areas) consists of potentially most dangerous organisms. Such organisms are responsible for the occurrence and spread of water-borne diseases.

Sewage treatment is meant the various steps undertaken in the process of transferring sewage into a harmless liquid. That is to render sewage inoffensive without causing nuisance or odour and to reduce or eliminate any possible contaminations of water supplies, bathing areas, etc., by the untreated or un-disposed sewage.

27.4.2 Sanitary Fittings and Appliances

Sanitary fittings and appliances comprise of traps, water closets, flushing cisterns, etc., which are discussed below.

1. Traps

Traps are fittings which are installed in drainage pipes to prevent the passage of foul air or gases through drains, waste or soil pipes. This is possible because traps are equipped with water seals having a minimum depth of 25 mm. Higher the depth greater the effectiveness of trap. Depth varies in practice from 25 to 75 mm and 50 mm depth is quite common.

Qualities of good traps are:

  1. They should have adequate water seal at all times which is possible only when they are non-absorbent.
  2. There should not be any projections which may obstruct or retard the flow of water. Further it should be smooth.
  3. They should retain minimum quantity of water consistent with providing deep water seal with large area.
  4. Apart from self-cleansing, provision should be there for cleaning manually or otherwise.

Traps are classified based on shape as R-trap, Q-trap and S-trap and based on use as floor trap, gully trap and intercepting trap.

Figure 27.1 of traps based on shape.

Figure 27.1 Traps based on shapes (P-Q-S)

Floor traps are intended to collect surface wash or wastewater from the floors of the bath and kitchen. These are provided with cast iron grating at top so as to retain coarse solid matter. Thus preventing the matter to go along with wastewater and thereby cause blockade (Fig. 27.2).

Figure 27.2 Floor trap

Gully traps are intended to receive sullage water from baths, sinks and washbasins. Further they are also used to receive rain or surface water from house-tops or back yards. The water seal is 50–75 mm. Waste pipes and rain-waste pipes are invariably connected to drains through the gully trap (Fig. 27.3).

Figure 27.3 Gully trap

Intercepting traps or also called as interceptors. These are installed at the junction of the house drain and house sewer. The primary object is to prevent the foul gases in the public sewer entering the house drainage system (Fig. 27.4).

2. Water Closets

Water closet is a water-flushed-plumbing figure designed to receive human excreta directly from the user. There are two types of water closets, viz., Squatting or the Indian type and pedestal or the European Type. Figures 27.5(a) and (b) show the two different types.

Figure 27.4 Intercepting drain

Figure 27.5 Water closets

(i) Indian Type

This has a squatting pan of 45–63 cm in overall length and 45–50 cm in height. The W.C. is connected to soil pipe through a P-trap or S-trap.

(ii) European Type

It is a wash down water closet provided with a seat and cover and fitted with P-trap and S-trap. It has a maximum overall height of 63 cm and a height of 34–40 cm.

Both the types of WCs are provided through flushing cisterns and flushing pipes.

3. Flushing Cistern

This is a sanitary appliance which is used flushing out water closets, urinals, etc. There are two types one is valveless siphonic type and the other is valve-fitted siphonic type. The former is preferred and largely used in practice.

4. Washbasins

Washbasin is also called as lavatory basin. It is made of white-glazed earthen wave, enamelled iron, etc. There are two types, viz., flat back and angle back. Washbasins are fixed either on brackets secured to the walls or on pedestals rising from the floor.

5. Sink

It is a rectangular shaped receptacle used in kitchen or laboratory for draining of water. It is to be located as far as possible near a window so as to get adequate light. The height from the floor is about 90 cm to the top edge of the sink.

6. Urinals

There are two types, viz., bowl type and the slab or stall type. Both the types are flushed through siphonic type of flushing cisterns. In the bowl type, the cistern may be hand operated and of 5 l capacity. In the stall type the automatic flushing cisterns are used.

27.4.3 Plumbing System of Drainage

Plumbing system of drainage is one through which discharge from sanitary fixtures or appliances is conveyed. The three principal systems are single stack system, the one-pipe system and the two-pipe system.

1. Single Stack System

In this system all waste matters such as from bath, kitchen and sink and foul matter from urinals or excreta from water closets are discharged into a single soil pipe. This pipe also acts as a ventilating pipe. In this system complete reliance is built entirely on the effectiveness of water seal with the assurance that the entry of gases from sewers are blocked. The advantages of the system are:

  1. Simplicity in design, layout and easy plumbing of sanitary fixtures.
  2. Better external appearance of the building.
  3. More compact system and
  4. More economical.

The main disadvantage with this system is easy breaking up of water seal in taps.

2. One-Pipe System

In this system separate vent pipes are provided. All the traps of water closets, basins, baths etc., are adequately ventilated to preserve the water seal. In this system a caged dome is provided projecting above the roof top such that to allow a natural outlet to the foul gas. This system requires a difficult arrangement of pipe work and also costlier than the single-stack system.

3. Two-Pipe System

In this system all soil appliances such as water closets and urinals are connected to a vertical soil pipe. All wastewater appliances such as baths, washbasins, sinks, etc., are connected to separate waste pipe which is disconnected from the drain by means of a gully trap. Thus in this system there are two sets of vertical pipes, viz., the soil pipe and the waste pipe, each one is provided with a vent pipe. This system is the best plumbing system which is most efficient in the conveyance of sanitary waste and also largely favoured for adoption. However, this is the costliest of all systems.

27.4.4 Layout of Building Drainage

The following aspects have to be considered in the design and construction of a drainage layout:

  1. This layout should be simple.
  2. All pipes should be laid in straight lines both in horizontal and vertical directions.
  3. Abrupt changes in the direction of pipeline may affect the natural flow.
  4. In the points of intersection of pipes and wherever bends occur, it is essential to provide inspection chambers or manholes.
  5. The contained angle between the intersecting pipes should be less than 45° so as to ensure a gradual and smooth flow.
  6. Sewers should not be ordinarily laid under a building. If it is inevitable a cast iron pipe should be laid in straight reach with a uniform gradient.

27.4.5 Pipes for Drainage

1. Pipes and Gradients

Pipe sizes for house drains and sewers are 100, 150 and 230 mm and in some cases 300 mm. In order to avoid deposition of solid matter, the pipes should be laid as per the recommendation of I.S. Code (IS: 1742–1972), Table 27.4.

Table 27.4 Recommended gradient of sewer discharge pipes

Source: IS: 1742–1972.

2. Positioning of Pipes

The following points shall be kept in view while deciding the positioning of pipes:

  1. All soil pipes, waste and ventilating pipes should be conveniently grouped in shafts or ducts with adequate capacity. This provision is needed to allow for inspection and repair work.
  2. All the pipes needed for different purposes have to be adequately provided for during the construction stage itself at their appropriate positions.
  3. When pipes are not embedded it should run clear of the wall with a minimum clearance of 5 cm.
  4. Waste pipes are to be separated from the house drains by using gully traps. This arrangement is essential to prevent entry of foul air or gas, vermin, etc., into the building.
  5. The soil, waste and vent pipes should be vertically carried above the top of the building. They are to be covered by copper, plastic or galvanised iron wire domes. The arrangement is needed to prevent nesting of birds or inadvertent falling in of objects inside the pipe.
  6. Diameter of pipes used for various purposes are given below (Duggal, 1988)

    (a) Soil pipe 100 mm

    (b) Waste pipe – horizontal 32–50 mm

    (c) Waste type, vertical 75 mm

    (d) Vent pipe 50 mm

    (e) Anti-siphonage pipe:

    Connecting soil pipe 50 mm

    Connecting waste pipe 40 mm

27.4.6 Sludge and Effluent Disposal

Sedimentation is carried out with the object of removing such suspended mineral and organic matter from sewage. Sedimentation tanks are units in which sedimentation is brought about. The lighter organic sewage solids which settle in the sedimentation tanks are termed as sludge. The sewage that has been partially classified by the settling out of the solids is known as the effluent.

In a general set up the disposal of sludge can be done by adopting any one of the following methods:

  1. Dumping into waste bodies
  2. Shallow Burial
  3. Lagooning
  4. Mechanical dewatering and
  5. Drying in Beds

If such a general disposal system is not available one has to go in for a sedimentation tank. Generally sedimentation tank adopted is a septic tank which is a horizontal continuous flow sedimentation tank. A description of septic tank is explained in next section. The putrescible and highly odorous efficient from the septic tank requires to be properly treated and disposed of sub-surface irrigation field method or discharging into other soil absorption system such as soak pit and leading cell pool which is described later.

1. Septic Tank

A septic tank is a horizontal continuous flow sedimentation tank. Here the sewage is allowed to move very slowly so as to retain for a period sufficient to develop 60–70% of suspended matter to settle in the form of sludge. Lighter solids float to the surface and combine with grease and fat and form floating scum. The scum and sewage are allowed to stay for a period of 7 months during which period complete decomposition takes place through a process called sludge digestion. The volume of sludge also gets reduced for easy disposal. The effluent from septic tank has very bad colour. It is dark in colour with fine solid particles and has to be disposed with utmost case. A schematic layout of a septic tank is shown in Fig. 27.6.

Figure 27.6 Septic tank

A septic tank is constructed in such a way so as to prevent direct current between the inlet and the outlet. This provides a better sedimentation and is achieved by using T-pipes with submerged ends as inlet and outlet. As an alternative, baffle walls may be provided. The T-pipe or the baffle at the outlet also helps in retaining the scum in the tank. Certain quantity of scum is needed to hold-back odours and to create a form of heat insulations which in turn aids the bacterial action. Usually a manhole is fixed on the RCC cover slabs. The tank cover allows to keep the sewage warm, lessening odour, etc. Gases are separately removed through a vent pipe. Sludge is removed periodically.

Septic tanks are to be located at a place which is exposed to sky and accessible for cleaning. The sewage in a septic tank can be taken as only a primary treatment effect. Before disposal the effluent needs a secondary treatment. The septic tank has only a restricted use in practice, such as schools, hospitals, small residential colonies and other public institutions where sewers are not yet laid.

2. Soak Pit and Leaching Cess Pool

The putrescible and highly odorous effluent from the septic tank requires to be properly treated and disposed. The methods of disposal are:

  1. Sub-surface irrigation employing absorption field method.
  2. Discharge into other soil absorption system as soak pit or seepage pits and leaching cess-pools.

Sub-surface irrigation is also termed as land infiltration. It is the application of sewage or its effluent into the land through a system of open-jointed pipes or drains placed near the surface of the ground and thereby enabling the effluent to percolate into the surrounding soil.

A soak pit is a covered pit through which the effluent is allowed to be soaked or absorbed into the surrounding soil. The pit may be empty or filled up with brick or stone aggregates (Fig. 27.7).

1. Brick lining with dry joints

2. Outer casing with coarse aggregates (7.5 cm thick min)

Figure 27.7 Soak pit

A leaching cesspool is a pool such that the top portion acts as an absorption field and the bottom as a septic tank. This is done by providing open-jointed lining at the upper portion which enables the sewage effluent to the easily dispersed to the surrounding soil. The bottom portion is of solid wall which functions as a septic tank (Fig. 27.8).

1. Outer casing with coarse sand (30 cm thick).

2. Lining with coarse aggregate (15 cm thick).

3. Brick work with mortar joints.

Figure 27.8 Leaching cesspool

27.5 ELECTRICAL SUPPLY

Electrical power is provided to the building by the Government. Electricity is distributed in small towns and villages by overhead wires. But in large cities and towns the distribution is done through underground cables. The supply of electricity is including the cables up to the electric metre. In order to isolate the main supply from the building, a system of fuses is installed between the supply inlet and the electric metre board. From the fuses, the wires are led to the metre and from there to the consumer unit. From this point the electricity is distributed to the various parts of the building. It is the responsibility of the owner of the building to provide wiring and other fixtures from the metre to the distribution board and other parts of the building (Varghese, 2012).

27.5.1 Single and Three-Phase Supply

The electricity from the sub-stations are stepped down through local transformers and supplied to nearby buildings as single-phase or three-phase supply (50 cycles per second at 220 volts between the phase and the neutral). Then the supply is 230 volts between a phase and a neutral and it is volts between the phases. In a single-phase supply, there shall be one live-phase wire and a neutral. In a three-phase supply, there shall be three live phases and a neutral.

When the electrical power load is small and the total current drawn is less than 30 amp, a single-phase may be sufficient. That is only for lighting and use of fans a single-phase may be enough. However, when the load is heavy, as when use of many equipment such as air conditioners, cooling ranges, etc., it is necessary to draw current from three live phases and a neutral. The electric current metre for a three-phase supply is different from that of single-phase. It is a condition that all equipment used in residences must be 220–230 volts.

Instead of underground cable, if supply is drawn from overhead insulated cable special care has to be taken. In this case it is to be first run down the walls with insulated cables and then turned up at the entry point of the building to prevent rainwater running along the cable into the electric board.

27.5.2 Distribution Circuits

In an ordinary building, for distribution of electricity from the consumer control unit to other points, the supply is divided into three separate types of circuits, viz.,

  1. Lighting circuit of low capacity
  2. Power circuit through ring circuit
  3. Fixed appliance circuits

Red wires are used for the live wire whereas the neutral is black or blue and earth wires are green and yellow. In the circuit a phase changer may also be incorporated.

27.5.3 Materials and Devices Used in Wiring

Following are the materials and devices used in the wiring of a building.

1. Cables

Cables consist of copper of aluminium conductors surrounded by insulation. Aluminium conductors are used to reduce the cost but they are inferior in quality compared to copper cables. Now-a-days stranded wires are commonly used for better performance.

Rubber or PVC insulation may be made. In moist or wet conditions PVC insulation may fare better than rubber.

2. Fuses

Basically a fuse protects appliances and cables from damage by electrical faults. The current rating of fuses should be lower than that of the cable it has to protect. Two types of fuses are in use, viz., Rewirable or semi-enclosed fuses and cartridge fuses.

3. Miniature Circuit Breaker

Now-a-days miniature circuit breakers (MCB) are used instead of fuses. Miniature circuit breakers are single pole switches which automatically switches off when excess current flows. An MCB trips at 1.25 times its rated current capacity. It is only an overload device. But for the initial cost it has many advantages.

4. Earth Leakage Circuit Breaker (ELCB)

An electric appliance with a fault is connected to a line and if the metal parts are not earthed the metal may become live without the fuse blowing. Such a situation may cause a shock to the person touching it. On the other hand, if the metal body is earthed, then current will flow through the earth wire. In such a condition, it is advisable to use a tripping device called the earth leakage circuit breaker. It automatically trips even where a small current flows through the earth wire. This switch is connected to the neutral line of the electric supply. When it trips, the supply to the building will be completely cut off.

5. Residual Current Circuit Breaker (RCCB)

This type of breaker is much more positive protection device which can be provided instead of earth leakage circuit breaker to avoid electric shocks and current leakages. An RCCB is connected to all the three phases and the neutral. It is more expensive but provides excellent protection.

27.5.4 Wiring of Buildings

The following are three types of wires:

  1. Sheathed wiring by surface fixing
  2. Conduit installation on walls and ceilings
  3. Concealed conduit wiring

Now-a-days in most of the buildings concealed PVC conduit wiring is used. The PVC conduits may be laid on the surface or concealed. In both the cases care has to be taken to see that no water enters the pipes. In the case of concealed pipe, it is safe to surround the conduit in chicken mesh reinforcement.

SALIENT POINTS
  1. Plumbing services in the entire system of piping, fixtures, applications, etc., for providing water supply or drainage to a building or premises.
  2. A plumbing water supply system consists of water supply and distribution with the use of pipes, control valves, pipe layout, storage tanks, etc.
  3. A plumbing drainage system consists of collection and disposal of wastewater with the use of water closets, urinals, traps, vents, anti-siphonage pipes, house drains, house-sewers, etc.
  4. Where municipal water supply is not available water is obtained from wells as in villages and in small towns. In large towns and cities, municipal water supply is available through street mains. In both the cases the water may be pumped to an overhead tank from which the entire water distribution can be taken care of. In case the pressure in mains is less a sump may be provided.
  5. Capacity of an overhead tank is based as the number of persons using it. It is usually of 200–500 l.
  6. Water distribution system needed for a conventional residential building depends on the following aspects.

    (i) Estimation of water requirement.

    (ii) Determination of pipe sizes.

    (iii) Pipe layout principles.

  7. As per Indian Code recommendations for residences 135 l of water per head per day to be used for the design of water supply system.
  8. In general for a middle class house the average number of pipes needed shall be about eight and pipes of minimum nominal size of 20 mm diameter are enough.
  9. Two main types of pipes are Galvanised-iron pipes (GI pipes) and unplasticised polyvinyl chloride (UPVC) pipes.
  10. Traps are fittings which are installed in drainage pipes to prevent the passage of foul air or gases through drains, waste or soil pipes.
  11. Traps are classified based on shape as P-trap, Q-trap and S-trap and based on use as Floor trap, Gully trap and Intercepting trap.
  12. Floor traps are intended to collect surface wash or wastewater from the floors of the bath and kitchen.
  13. Gully traps are intended to receive sullage water from baths, sinks, and washbasins. They are also used to receive rain or surface water from the house tops or back yards.
  14. Intercepting traps are also called as interceptors and are installed at the junction of the house drain and house sewer.
  15. Water closet is a water-flushed-plumbing fixture designed to receive human excreta directly from the user. There are two types, viz., squatting or the Indian type and Pedestal or the European type.
  16. Flushing cistern is a sanitary appliance which is used flushing out water closets, urinals, etc.
  17. Plumbing system of drainage is one through which discharge from sanitary fixtures or appliances is conveyed. The three principal systems are single stack system, the one-pipe system and the two-pipe system.
  18. In the single stack system all waste matters such as from bath, kitchen and sink and foul matter from urinals or excreta from water closets are discharged into a single soil pipe.
  19. In the one-pipe system separate vent pipes are provided. All the traps of water closets, basins, baths, etc., are adequately ventilated to preserve the water seal. In this system a caged dome is provided projecting above the roof top such that to allow a natural outlet to the foul gas.
  20. In the two-pipe system all soil appliances such as water closets and urinals are connected to a vertical soil pipe. All wastewater appliances such as baths, washbasins, sinks, etc., are connected to separate waste pipe which is disconnected from the drain by means of a gully trap. Thus in their system there are two sets of vertical pipes, viz., the soil pipe and the waste pipe, each one is provided with a vent pipe.
  21. In a general set up the disposal of sludge can be done by adopting any one of the following methods:

    (i) Dumping into waste

    (ii) Shallow burial

    (iii) Lagooning

    (iv) Mechanical dewatering

    (v) Drying in beds.

  22. A septic tank is a horizontal continuous flow sedimentation tank. Here the sewage is allowed to move very slowly so as to retain for a period sufficient to develop 60–70% of suspended matter to settle in the form of sludge.
  23. The putrescible and highly odorous effluent from the septic tank requires to be properly treated and disposed. The methods of disposal are

    (i) Sub-surface irrigation employing absorption field method.

    (ii) Discharge into other soil absorption system as soak pit or seepage pits and leaching cell pool.

  24. A soak pit is a covered pit through which the effluent is allowed to be soaked or absorbed into the surrounding soil. The pit may be empty or filled up with brick or stone aggregates.
  25. A leaching cesspool is a pool such that the top portions acts as an absorption field and the bottom as a septic tank.
  26. Electrical power is supplied as single phase or three-phase supply. In a single-phase supply, there shall be one line-phase wire and a neutral. In a three-phase supply there shall be three line phases and a neutral.
  27. For distribution of electricity from the consumer control unit to other points, the supply is divided into three separate types of circuits, viz.,

    (i) Lighting circuit of low capacity

    (ii) Power circuit through ring circuit

    (iii) Fixed appliance circuits.

REVIEW QUESTIONS
  1. How the water requirement of a building is assessed? What is the requirement for a residential building?
  2. Why it is necessary to store water in case of residential building?
  3. List the various appliances used for water supply in a residential building.
  4. What is meant by a backflow? How it is prevented in the layout of water supply pipes in a residence.
  5. How the sizes of pipes are selected for water distribution in a residential building?
  6. What are traps? Why is it necessary that all sanitary fittings should be provided with individual traps?
  7. Explain the one- and two-pipe systems of plumbing and state their specific use.
  8. How effluents are discharged?
  9. What is a septic tank? How is it effectively used in a residence?
  10. Explain soak pit and leaching cesspool.
  11. Distinguish between a one-phase and two-phase systems.
  12. Explain the materials and devices used in wiring of a building.
  13. Distinguish between Miniature circuit Breaker and Earth Leakage circuit breaker.
  14. Explain Residual Current Circuit Breaker.
  15. Bring out the advantages of concealed wiring.