BS 8005-1:1987 download free.British Standard Sewerage Part 1 . Guide to new sewerage construction.
This Part of BS 8005 provides guidance on the materials, design, construction, testing, surveying, operation and maintenance and repair of new sewers.
NOTE. The titles of the publications referred to in this standard are listed on the inside back cover.
Other standards publications not referred to in this standard, but dealing with closely associated subjects, are listed in appendix A. References are made to other sources of authoritative information. These will be found throughout the text, indicated by bracketed numbers thus (21) and are listed in appendix B.
2 Definitions
For the purposes of this Part of BS 8005, the definitions given in BS 892, BS 4118, BS 6100 and BS 8005: Part 0 apply, together with the following.
2.1 catchment area. The area of a watershed discharging to a sewer, or watercourse.
2.2 flow attenuation. The process of reducing the peak flow rate in a sewer system by redistributing the same volume of flow over a longer period of time.
NOTE. This can be achieved by on or oft line storage within the sewerage system, or by above ground storage before flows enter the sewer.
2.3 inverted siphon. A pipe or conduit where the soff it drops below the hydraulic gradient and in which the sewage flows under pressure of gravity.
2.4 nominal size IDN). A numerical designation of the size of a pipe, bend or branch fitting, which is a convenien round number approximately equal to a manufactured dimension.
NOTE. ‘Nominal bore’ Is the approximate internal diameter of a unit as declared by the manufacturer. This quantity is quoted with units (mm) whereas nominal size (DN) is quoted without units.
2.5 percentile peakedness. The departure from the mean value of a storm profile, expressed as a percentage.
2.6 rainfall. Natural precipitation of water in any form, such as rain, snow, hail, etc., the rate of which is measured in millimetres of water per hour.
2.7 renovation. Methods by which the performance of a length of sewer is improved by incorporating the original sewer fabric, but excluding maintenance operations such as isolated repairs and/or silt removal.
2.8 roughness value (K5). A measure of the resistance of the surface of a pipe or channel under turbulent flow which is expressed in millimetres.
NOTE. This value is based on the diameter of uniformly graded sand grains which would give the same resistance to flow.
Structure plans and local plans can assist the planning and design of new, improved and extended sewerage systems. The allocation of land use and the policies for development should be determined for each catchment area. This information will influence the assessment to be made of the extent of impervious areas and the consequent calculation of surface water runoff, and will provide assistance to forecast population changes and foul sewage flows
The planning horizon will inevitably differ from the various potential lifespans of the many sewers and associated structures within the catchment area. Sewerage planning and design should take account of the impact of changing land use and future alternative developments.
4.2 Population and water usage statistics
4.2.1 Population statistics. An accurate assessment of population is essential in determining the probable flows in a sewerage system.
The official statistics of the Registrar General refer to areas defined by local authority boundaries, but are useful as a check on estimates made by other means. Planning statistics can be of assistance since they frequently give local information on the average occupancy rate of domestic dwellings. When multiplied by the number of residential properties obtained by physical count, these can provide a fairly accurate assessment of population. In holiday resorts or other areas where there is an occasional or seasonal influx of people, such a means of estimating is not possible. Peak population may be assessed only by sampling typical areas during the holiday or peak season and extending the densities thus estimated to the whole area under consideration. Registers of accommodation maintained by many local authorities, Tourist Boards. etc., together with information that can frequently be obtained from the loCal planning department, may be of value. Where provision needs to be made for future population in areas not yet developed or due for redevelopment, information should be available from the local planning authority on areas scheduled for development and on the scale and intensity of development intended. Planning policies are subject to regular review and the designer should consult the local planning authority to assess the likelihood of future changes in policy.
4.2.2 Water usage statistics. The water supply authority can provide a fairly accurate assessment and forecast of the conwmption of water in any particular area; this will have a direct relationship to the likely flows for foul sewerage purposes.
Commercial and industrial premises and public buildings such as hospitals and schools, which obtain a supply of water from public sources, are usually metered. After making due allowance for water use in any industrial process, the figures of consumption can provide a useful guide to the anticipated flows of waste likely to arise from such premises.
Some private and commercial undertakings obtain water direct from private abstractions from rivers, canals, wells or boreholes; these should be taken into account in assessing the possible discharge of foul sewage.
5.2.2.6 Grey iron pipes. Grey iron pipes and fittings should comply with BS 437 and with BS 4622 and are manufactured in the size range ON 50 to DN 225; BS 437 makes provision for centrifugally cast pipes with flexible joints in lengths up to 5.5 m. Flexible joints for these pipes should comply with BS 6087.
Pressure pipes and fittings with flexible or flanged joints should comply with BS 4622. Pipes with flexible joints are available in 5.5 m lengths and those with flanged joints in 4 m lengths.
Fittings complying with BS 437 can be jointed directly to BS 4622 pipes with lead caulked joints in the smaller diameters (DN 100 and DN 150 only).
5.2.3 Flexible pipes
5.2.3.1 General. Flexible pipes deform under load and the extent of this deformation depends upon the stif’ness of the pipe and the compaction of the immediate surround fill. The materials for these pipes show ductile stress-strain characteristics.
5.2.3.2 Corrugated metal pipes. Corrugated metal pipes are manufactured in steel in diameters from ON 150 to DN 2600 and in lengths from 6 m to 9 m. They are jointed by corrugated or dimpled coupling bands and various types of bituminous coatings are available. These pipes are not covered by a British Standard and details should be obtained from the manufacturers. Two forms of corrugation are available for the pipe as follows.
(a) Helically corrugated pipes, available in sizes from
DN 150 to DN 1500 made from galvanized steel sheet
complying with BS 2989, grade Z2. coating type G600.
The helical joint is formed by a locked seam.
(b) Annularly corrugated pipes, available in sizes from DN 1000 to DN 2600 made from steel complying with BS 1449: Part 1. grade 3. condition HR. Longitudinal joints are rivetted and the pipes are galvanized in accordance with BS 729.
5.2.3.3 Ductile iron pipes. Ductile iron pipes and fittings should comply with BS 4772 and are manufactured in a range from DN 80 to DN 1600. Ductile iron pipes with flex ible joints are manufactured in nominal lengths of 5.5 m for DN 80 to DN 800 inclusive and nominal lengths of 8 m for DN 900 to DN 1600 inclusive. Ductile iron pipes are suitable for both pressure and non-pressure applications. A class of pipe (class K9) is available for general purposes but other classes can be supplied. Pipes with flanged joints are manufactured in 4 m lengths.
5.2.3.4 Un flanged corrugated liner plates. Unflanged corrugated liner plates are generally used to form culverts pedestrian tunnels and similar structures which are
BS 4772 details the standard protection for ductile iron pipes. In sizes DN 80 to ON 800 the pipes are zinc coated externally, prior to bitumen coating internally and externally. For sizes ON 900 to DN 1100 the pipes are cement mortar lined and coated externally with bitumen material. All size pipes and fittings can, if required, be cement mortar lined. The bitumen should comply with BS 3411, type H or BS4147 type I.
5.17.4 Protection for grey iron pipes. The standard protection for grey iron pipes is as follows:
(a) cold applied coatings complying with BS 3416; or
(b) hot applied coatings complying with BS 4147; or
(c) zinc or epoxy type coatings as described in BS 5493.
NOTE. In some .ggreuive soils or where aggressive chemicals are being d*scharged it may be advisable to use additional protective coating systems or combinations of those listed above.
5.17.5 Protection for steel pipes. BS 534 describes internal and external protection systems for steel pipework for sewerage.