The document discusses various materials used for sewer construction including brick, concrete, precast concrete, cast-in-situ concrete, stoneware, asbestos cement, cast iron, steel, ductile iron, UPVC, HDPE, GRP, FRP and pitch fibre pipes. For each material, the key advantages and disadvantages are described. The document also provides the relevant Indian Standard specifications for each material. Crown corrosion of concrete sewers is explained as being caused by the formation of sulfuric acid due to the action of sulfate reducing bacteria on hydrogen sulfide gas in stagnant sewage flow at the bottom of sewers.

1. Materials of Sewer

2. Brick
• Used particularly for large diameter
sewers
• Advantage-
– Can be constructed to any
required shape and size
• Disadvantage-
– higher cost
– Slow work progress
– Larger space requirement
• Cement concrete or stone invert
• To prevent ground water infiltration:
– plaster outside surface with
mortar using sulphate resistant
cement
– inside surface mortar + high
alumina cement (IS 6452) or
polyurea coating.

3. Concrete
• Advantages
– Relative ease with which
required strength may be
provided
– Wide range of pipe sizes
– Rapid trench backfill
• Disadvantages
– crown corrosion by sulphide
gas
– mid depth water line corrosion
by sulphate
– outside deterioration by
sulphate from soil water

4. Precast concrete
• Commonly used for branch and main sewers
• Two types
– Non-pressure pipes
• used for gravity flow (sewers running
partially full)
• Plain (I.D. 80mm-450mm; thickness:
25mm-35mm) (NP1)
• Reinforced (I.D. 80mm-2600mm;
thickness: 25mm-215mm) (NP2, NP3 &
NP4)
– Pressure pipes (P1, P2 & P3)
• used for force mains, submerged
outfalls, inverted siphons and for gravity
sewers where absolute water-tight joints
are required.
• Reinforced (I.D. 80mm-1200mm;
thickness: 25mm-120mm)
• Length : 2-3m
• These pipes have plain ends or spigot and socket
ends.

5. Cast-in-situ Reinforced Concrete
• constructed where they
are more economical
• when non-standard
sections are required
• when a special shape is
required
• when the headroom
and working space are
limited.

6. Stoneware or Vitrified Clay
• normally available in lengths of 90 cm
• Skilled labour required for caulking the
joints with yarn soaked in cement mortar
and packing in the spigot and socket
joints
• Classes
– AA: 100% hydraulic testing of pipes to
be carried out in manufacturing stage
– A: 5% of the pipes to be tested by
following IS 651
• Resistant to most acids and to erosion
due to grit and high velocities
• A minimum crushing strength of 1,600
kg/m is adopted for all sizes
• Special bedding or concrete cradling
required to improve field supportive
strength

7. Asbestos Cement
• usually used in sizes ranging from 80 mm to 1000 mm
in diameter
• Advantages
– Non corrosiveness to most natural soil
conditions,
– freedom from electrolytic corrosion,
– good flow characteristics,
– light weight,
– ease in cutting, drilling, threading and fitting with
specials,
– allowance of greater deflection up to 12 degrees
with mechanical joints,
– ease of handling,
– tight joints and
– quick laying and backfilling are to be considered
• Disadvantages
– subject to corrosion by acids, highly septic
sewage and by highly acidic or high sulphate soils
– Cannot stand high super imposed loads and may
be broken easily

8. Cast Iron
• Available in diameters from 80 mm to 1050 mm
and are covered with protective coatings
• supplied in 3.66 m and 5.5 m lengths
• A variety of joints are available including socket,
spigot, and flanged joints.
• Classified as LA, A and B according to their
thickness. Class LA pipes have been taken as the
basis for evolving the series of pipes.
• Application: Cast iron pipes with a variety of
jointing methods are used for pressure sewers,
sewers above ground surface, submerged outfalls,
piping in sewage treatment plants and
occasionally on gravity sewers where absolutely
water-tight joints are essential or where special
considerations require their use.
• Advantage: long laying lengths with tight joints,
ability when properly designed to withstand
relatively high internal pressure and external loads
and corrosion resistance in most natural soils.
• Disadvantage:
– corrosion by acids or highly
septic sewage and acidic soils
– the amount of deflection
allowed should not normally
exceed 2.5 degrees for lead
caulked joints.
• Inside coating shall be by Cement
mortar and outer coating shall be
coal tar

9. Steel
• Pressure sewer mains, under water river
crossings, bridge crossings, necessary
connections for pumping stations, self-
supporting spans, railway crossing and
penstocks are some of the situations where
steel pipes are preferred
• Advantages
– withstand internal pressure, impact load
and vibrations much better than CI pipe.
– more ductile and withstand water hammer
better.
• Disadvantage
– cannot withstand high external load
– main is likely to collapse when it is
subjected to negative pressure
– susceptible to various types of corrosion
• Inside coating by high alumina cement mortar
or polyurea and outside by epoxy.
• Steel pipes shall conform to IS 3589. Electrically
welded steel pipes of 200 mm to 2,000 mm
diameter should conform to IS 5822.

10. Ductile Iron Pipes
• made by a metallurgical process, which involves
the addition of magnesium into molten iron of low
sulphur content.
• The ductile iron pipes are usually provided with
cement mortar lining at the factory by centrifugal
process to ensure a uniform thickness throughout
its length
• available in the range of 80 mm to 1000 mm
diameter, in lengths of 5.5 to 6 m
• Advantages
– excellent properties of machinability,
– impact resistance,
– high wear and tear resistance,
– high tensile strength and ductility and
– corrosion resistance.
– strong, both inner and outer surfaces are
smooth,
– These pipes are approximately 30 % lighter
than conventional cast iron pipes

11. Non-Metallic Non-Concrete
Synthetic Material Pipes

12. UPVC Pipe (unplasticized
polyvinylchloride )
• Advantages
– resistance to corrosion,
– light weight for transportation,
– toughness, rigidity,
– economical in laying, jointing, and
maintenance and
– easy to fabricate
• IS 15328 deals with non-pressure
unplasticized polyvinylchloride (PVC)
for use in underground sewerage
system. IS 9271 deals with the
unplasticized polyvinyl chloride
(UPVC) single wall corrugated pipes
for drainage.

13. High Density Polyethylene (HDPE)
Pipes
• Advantages
– Offer smooth interior
surfaces and
– relatively higher resistance to
corrosion
– they are available in solid wall
– When laid in straight
gradients without humps or
depressions, they can easily
offer longer life cycle
• joints are usually fusion
welded or flange jointed
depending on straight runs
or fittings

14. Structured Wall Piping
• These pipes can be manufactured
in PVC-U, PP and PE as per EN
13476-3 / IS 16098
• These pipes are either double
walled or ribbed walled
• The Type B pipes are generally
known as Double Walled
Corrugated (DWC) pipes.
• In India, DWC pipes are produced
in sizes 75 mm ID to 1,000 mm ID
with a standard length of 6 m for
easy transportation and handling
and to reduce the number of
joints required.

15. Glass Fibre Reinforced Plastic Pipes
(GRP)
• widely used in countries
where corrosion resistant
pipes are required at
reasonable costs
• GRP can be used as a lining
material for conventional
pipes which are subject to
corrosion.
• Fibre glass can resist external
and internal corrosion
whether the corrosion
mechanism is galvanic or
chemical in nature.

16. Fibre Glass Reinforced Plastic Pipes (FRP)
• FRP is a matrix or composite of
glass fibre, polyester resin and
filters.
• These pipes possess better
strength, durability, high tensile
strength, low density and are
highly corrosion resistant.
• Fibre-glass pressure pipes are
manufactured in diameters up
to 2,400 mm and length up to
18 m.

17. Pitch Fibre Pipes
• These are pitch impregnated fibre pipes
• Advantages
– light in weight
– Durable
– pipes can be easily jointed in any weather
condition as internally tapered couplings join the
pipes without the use of jointing compound
– flexible,
– resistant to heat, freezing and thawing and earth
currents, which cause electrolytic action.
– unaffected by acids and other chemicals, water
softeners, sewer gases, oils and greases and
laundry detergents.
– can be cut to required length on the site
• Application
– septic tanks and house connection to sewers,
farm drainage, down pipes, storm drains,
industrial waste drainage
• Available sizes: 50 to 225 mm nominal diameter and
length varying from 1.5 to 3.5 m
• Disadvantage
– susceptible to the
delamination of their inner
surface (blistering)
– susceptible to collapse under
applied loading sooner than
other pipes

18. Sewer material and corresponding standard specification
Material Standard specification Code
Brick (Inside plaster with mortar using high alumina
cement )
IS 6452
Concrete
Pre-cast concrete (Non-Pressure pipes) IS 458
Cast in-situ reinforced concrete (Concrete ) IS 456
Stoneware or vitrified clay (hydraulic testing) IS 651
Asbestos cement IS 6908
Cast Iron IS 1536 (spun pipe) and IS 1537 (vertically cast pipe)
Steel IS 3589
DI pipes IS 8329 (centrifugally cast DI pipes); manufactured
with ISO 9002 accreditation ; IS 9523 (DI fittings);
UPVC IS 15328 ( Non-pressurized); IS 9271 (single
walled corrugated pipe for drainage)
HDPE IS 14333
Structured wall pipe EN 13476-3 / IS 16098
GRP IS 14402
FRP -

19. Crown corrosion
With gradual deposition of organic and inorganic
matter at the bottom of the sewer, the flow of
sewage in lower layers become stale leading to
anaerobic conditions favourable for Sulphate
Reducing Bacteria which converts sulphate to H2S as
shown. Thiobacillus thioxidans convert H2S to
H2SO4. The suphuric acid deposited at the crown of
sewer reacts with concrete and forms CaSO4. Which
falls down as droplets making the crown of sewer
uneven and thinner. This phenomenon is known as
crown corrosion.