For a free flow
Rajiv Bhatia delineates new plumbing practices for house drainage, which form an essential building block of construction today

Providing environmentally safe sanitation to millions of people is a significant challenge, especially in the world’s second most populated country. The task is doubly difficult in a country where the introduction of new technologies can challenge people’s traditions and beliefs. Environmental sanitation, which evidently means cleaning of the environment, therefore, becomes a major task for a public health engineer, and this task primarily includes: collection and disposal of refuse and sewage from houses, buildings, and other public areas. The sewage produced in houses and buildings has to be conveyed and connected to the municipal sewers by owners of the houses. The provision and construction of an efficient plumbing system for collection and movement of the sewage produced in the building, till it is carried and discharged into the nearest municipal sewer, is an important aspect of building construction.

Many of us, who are living in areas provided with sewers, might have experienced the bad or improperly designed plumbing works, which poses problems everyday, in either the kitchen drains or the wash basin or the water-closet getting chocked, or the foul smell escaping from somewhere or the other. A properly-designed and carefully-constructed plumbing system, is, therefore, absolutely necessary to avoid such frequent troubles. Sanitary plumbing (house drainage system) may be defined as the installation, removal, renewal, repair and maintenance of pipes, including ventilation of those pipes and fittings to receive and convey sewage.

Drainage systems
The two major types of drains (pipes) are the sanitary drain, which receives the sanitary and domestic wastes, and the storm drain, which receives only that waste which is drawn off when it rains. Often the discharges from both these drains are kept separate (also called two-pipe system) and are drawn off to different terminuses -- the sanitary drain to the main sewer or septic tank and the storm drain to a nearby lake, river, or other natural drainage area. However, in many cases, both soil and storm stacks fall into a common or combination drain and flow together into the sewage system known as one-pipe system.

There are two types of drainage water: (i) Foul water (ii) Surface water.

Foul water consists of anything that comes from bathrooms, kitchens, utility rooms, car washing areas etc. This must always go to your foul water drain system. Surface water is rainwater only.

In older properties, the existing rainwater pipes are often discharged to the foul drain. This system is known as combined drainage. In a combined system, the rainwater pipes are discharged via gully traps, to stop foul air escaping from the drains. Modern systems keep the foul water and the surface water apart in separate drains. With this method, the rainwater is discharged either to a soak-away, watercourse or surface water sewer or to a rainwater harvesting system. Draining rainwater to these points does not create foul air. It is extremely important to ensure that you do not connect foul water to a surface water drainage system.

House drainage system
House drains are usually placed as soon as possible so the plumbers can work from the ground up as the building is being built. An underground drain is more economical and will not reduce the floor area. Cast iron pipe is recommended for most drains, especially those placed underground, but as in the case of the house sewer, both PVC and vitrified clay pipe have been used successfully.

Assuming that the method of disposing of sewage and drainage is decided upon, the problem of how to pipe the house safely may be considered.

No departure from a certain means of positively accomplishing a desired result should be accepted without unanimous endorsement of all stakeholders. People, however, are all too ready to accept any plan that promises saving of a few dollars. Certain plumbing accessories may be admirably adapted to use in one place, yet wholly unfit for service in another; but the manufacturers do not reveal this. It is the business of the public, through architects and plumbers, to select suitable means to the end. With the fresh-air inlet and proper installation throughout the building, an intercepting trap is likely to exclude sewer air from the house, and that keeps the drains in the house filled with fresh air from the open atmosphere. The intercepting trap being in the main line, all water from the house passes through it, insuring the water seal being maintained.

The soil and waste drainage pipes are also to be embedded in walls during construction. For this purpose, the location of seat, shower and wash-basin in each toilet should be decided before- hand and then their drainage should be aimed towards an external wall for further connection of floor traps and pipes to gully traps or inspection chambers.

Installation
The plumbing installation for the house itself begins with the laying of the house drain, which is the pipe that receives all waste and water discharged by the soil pipes and waste lines. This house drain is laid from a point just outside the building foundation wall where it connects to the house sewer, then through the wall, and either along or under the cellar floor to the point where connection with the soil stack is made. Before laying this drain, determine its overall length and how much pitch to give it so that it will drain as it should. The pipe itself may be laid section by section, but a better procedure is to fit three or four sections together outside of the trench and then set this longer section in at one time. Sections having Y fittings or change-of-direction fittings can also be prepared in this manner and then placed so that the fittings face in the proper direction.

Rain water pipes
The roof drainage plan should be prepared before raising the walls of the house and rainwater drainage pipes should be embedded accordingly in the walls. Always provide adequate slope to the roof towards the rainwater pipes. Openings of rainwater pipes must be covered with iron-gratings so that no debris or stone pieces fall and block them. Depending upon the area of roof, it may be divided into segments and slope of each segments and slope of each segment has to be aimed towards a rainwater pipe. Preference should be given to providing rainwater pipes in the walls near the recharge well of rain water harvesting system

Indian Standard Codal Provisions
I.S. 1742 ‘Code of Practice for Building Drainage’ is generally referred for planning and installation of effective and economical drainage system. This code gives recommendations for the terminology and various design parameters used, like choice of materials, fittings and sanitary appliances, design considerations, preparation and submission of plans, estimation of maximum flow of domestic sewage, excavation and layout, construction and maintenance of drains for waste water, surface water and sub-soil water and sewage, together with all ancillary works, like connections, manholes, inspection chambers, back filling, construction relating to conveyance of rain or storm water, etc., used within the building and from the building to the connection to a public sewer or to treatment works, a soak away or a water course. A special publication SP: 35 ‘A Handbook on Water Supply and Drainage’ (sections 6 and 7) also deal with various design parameters for installation of various sanitary appliances and their measurements.

National Building Code (NBC of 2005) in Part 9 deals with various aspects of water supply, drainage and sanitation of buildings.

Choice of material
PVC or CI pipes are used for sanitary work in house drainage work. These pipes are also concealed in walls and it is not possible to know their quality afterwards. CI pipes are of heavy and light type. For sanitary work, heavy CI pipes, also called HCI pipes, are used. Their weight is standardised for each diameter. The weight should be checked before purchasing CI pipes. These should also be checked against any cracks or weep holes. Such pipes create trouble during their use. Similarly, PVC pipes of varying quality are being produced by many manufacturers. These should be checked to be ISI marked, of required diameter, thickness and stiffness. PVC pipes are available in varying diameters and pressure retaining properties. For example, 4 inches diameter is available in 4 kg/cm2 and 6 kg/cm2 pressure ratings. Depending upon the requirement, one can choose from the range. Sometimes for less important works glazed stoneware pipes are also used with joints filled in cement mortar.

Pipe joints
Pipe joints are as important as the pipes themselves. If the joints are not water tight, even good quality pipes lose their purpose. In CI pipes, the joints are made by filling lead in the joints. Lead is costly material and there is a tendency amongst plumbers to save it, as the payment is always made to him for the number of joints. Similarly, joints in PVC pipes are adhesive or cement based solvent or heat welded or rubber gasket joints to check that full quantity of jointing material has been used in them and the joints made should be tested to be watertight.

Gradients
General requirements for gradient, in drainage pipes, as per CPWD specifications are:

• The discharge of water through a domestic drain is intermittent and limited in quantity and therefore, small accumulations of solid matter are liable to form in the drains between the building and the public sewer. There is usually a gradual shifting of these deposits as discharges take place.
  
• Gradients shall be sufficient to prevent these temporary accumulations building up and blocking the drains.
  
• Normally, the sewer shall be designed for discharging three times the dry weather flow flowing half-full with a minimum self -cleansing velocity of 0.75 meter per second. The sizes and slopes shall conform to local municipal bye-laws.
  
• In cases, where it is practically not possible to conform to the minimum gradients, a flatter gradient may be used but the minimum velocity in such cases shall on no account be less than 0.61 meters per second.
  
• On the other hand, it is undesirable to employ gradients giving velocity of flow greater than 2.4 meters per second. Where it is unavoidable, cast iron pipes shall be used.

Role of a plumber
A plumber is someone who maintains water piping and drainage systems in the home and in industry for a variety of purposes, such as drinking, drainage, heating, venting and sewage. Here are some vital skills needed if you want to be a good plumber:

• Good mathematical skills to interpret drawings and measure pipes accurately
  
• Good communication skills to tell customers and co-workers, what they are planning to do
  
• Good knowledge in welding, drafting, computer aided drawings
  
• Awareness about various plumbing codes and building regulations
  
• Good judgment to evaluate, before and after, all work is completed
  
• Sufficient knowledge about pipe materials to be used under various site conditions (eg CI, PVC, copper, stainless steel, composite pipes, etc.)
  
• Basic knowledge about electrical and digital operating fixtures (eg dishwasher, fully automatic washing machines, sensor based fixtures, etc)
  
• Good eye-hand coordination and spatial perception to complete work accurately and neatly
  
• Knowledge about various software and planning programs to keep a track of progress, location of pipes, fixtures and materials used
  
• Reading, drawings, and figures to understand the layout of waste, and venting systems
  
• Installing, repairing and maintaining domestic, commercial, and industrial drainage fixtures and systems
  
• Ability to work in confined spaces or at certain heights; locating pipe connections, passage holes, and fixtures in walls and floors; using hand and power tools, as well as machines, to measure, cut, bend and connect pipes;
  
• Ability to test pipes for leakages using water as well as air pressure gauges.
  
• Knowledge of legal restrictions and safety rules
  
• Ability to provide time and cost estimates of the work to be performed (both labour and materials).

Conclusion
With changing life styles and lavish spending has given sanitary plumbing a new dimension. Sustainable and eco-friendly design is the major focus of the building and construction industry. Consumers are increasingly educated regarding construction products and materials, resulting in a demand for more sophisticated and multifunctional products. Sanitary plumbing or house drainage layout is more than ever about green products that target low maintenance.

— Rajeev Bhatia is lecturer, Department of Civil Engineering, Mehar Chand Polytechnic College, Jalandhar

To read in print format subscribe to the magazine Download Subscription Form