Waste Disposal: Design & Connection of Plumbing Fixtures

PAUL HAY Capital Projects

www.phcjam.com

Waste Disposal: Design & Connection of Plumbing

Author:          Paul Hay

e-mail:             paul.hay@phcjam.com

profile:            www.linkedin.com/in/phcjam

1.0        DRAINAGE SYSTEMS NEED TO BE DESIGNED

1.1_          Each plumbing fixture provided with water supply must be drained.

1.2       Waste must be safely disposed of to prevent contamination.

1.2.1    Ventilation of the drainage system must be considered.

1.2.2    Gases must not be permitted to enter the building.

1.2.3    A disposal system must be chosen to suit the waste generated;

1.2.4    Disposal must not be close to sources of water; and 

1.2.5    Maintenance and inspection must be facilitated.

1.3       Recycling and the matching of water quality to usage can reduce the dependence on potable water and reduce drainage loads.

Figure 1:  Residential Drainage System  [Source:- AIA Architectural Graphic Standards, 1981]

2.0        FIXTURES MUST CONNECT TO A DISPOSAL SYSTEM

2.1       A waste fixture is a fixture designed for disposal of waste without assistance from flushing mechanisms.

2.1.1        Waste pipes connect waste fixtures to the drainage system.

2.1.2    A trap is a device which prevents the exhaust of drainage gases into the building.

                        2.1.2.1 Each plumbing fixture should have a trap.

2.1.2.2             Traps are generally located less than 600 mm from a fixture.

2.1.2.3             Water evaporates from traps that are infrequently used: floor drains being especially vulnerable to such occurrence.

Table 1:  Minimum trap sizes for plumbing fixtures  [Source:- National Building Code of Jamaica, 1983]

2.1.3    Trap ventilating pipe is a pipe connected to the outlet end of a trap terminating in an open end.

2.1.3.1             It prevents the water seal in the trap from being lost.

2.1.3.2             Vents are also necessary to allow fresh air entry into drainage systems and to exhaust gases already in the system.

            2.1.4    Trapped gully basins are open chambers that receive outflow from waste pipes.

2.1.5    Grease or interceptor trap is a device that prevents grease, petroleum products or other undesirable waste products from entering drains.

Table 2:  Minimum sizes for trap ventilating pipes  [Source:- National Building Code of Jamaica, 1983]

2.2       A soil fixture is a fixture designed for flush-assisted disposal of waste matter.

.                       2.2.1    Soil fixtures generally have built-in traps.

2.2.2    Soil pipes connect soil fixtures to a manhole

2.2.3    A manhole is an enclosed chamber that permits inspection and maintenance.

2.2.3.1             Manholes shall be no further than 50 m from the next manhole, or 15 m from a septic tank or other disposal system.

2.2.3.2             Where a manhole is located indoors, it shall be fitted with gas and water-tight cover.

2.2.4    A backdrop manhole is a manhole against which a vertical shaft has been constructed, on the side of the incoming drain, terminating in an easy bend before  entering the manhole.

2.2.4.1             It is used where there is an elevation difference between the inlet and outlet of a manhole in excess of 300 mm.

2.2.4.2             Access shall be provided to the vertical shaft to facilitate inspection and maintenance.

Table 3:  Drainage Fixture Units [Source:- JLC Field Guide to Residential Construction]

Table 4:  Stack and drain pipes sizes [Source:- National Building Code of Jamaica, 1983]

2.3       A branch pipe is a pipe connecting plumbing fixtures to a vertical stack.

2.3.1    Vertical stack is a vertical pipe terminating in a manhole or trapped gully basin.

2.3.2    A one-pipe system receives discharge from both waste and soil fixtures providing both traps are ventilated.

2.3.3    A two-pipe system separates discharge from waste and soil fixtures.

2.3.3.1             A vertical stack for waste fixtures terminates over a trapped gully basin.

1.3.3.2             A vertical stack for soil fixtures and one-pipe systems terminates in a manhole.

2.3.4    A branch drain connects a vertical stack or trapped gully basin to manhole.

2.4       A drain ventilating pipe is a pipe used to ventilate a drainage system: it connects to a manhole or branch drain at one end and terminates in an open end above the roof eaves.

2.5       A main drain is a pipe connecting manholes together or a manhole to a disposal system.

Table 5:  Maximum gradients for drain-pipes  [Source:- National Building Code of Jamaica, 1983]

FURTHER READING

National Building Code of Jamaica ,2^nd edition, Ministry of Finance & Planning, Ja., 1992.

Mechanical and Electrical Equipment for Buildings, 8^th edition, Benjamin Stein, John S. Reynolds, John Wiley & Sons Inc., USA, 1992;

Construction Materials & Processes, Don G. Watson, McGrawHill Book Co., USA, 1978;

Ramsey/Sleeper Architectural Graphic Standards, A^.I.A., Robert T. Packard (ed), John Wiley & Sons Inc., USA, 1981