7. Sewerage Works

SEWERAGE
RETICULATION

SYSTEM







WASTEWATER TREATMENT SYSTEM

DEFINITION

PURPOSE AND OBJECTIVES

❑ METHOD OF SEWER CONNECTION

• Most existing sewers that are shared by more than one property or lateral
drains (pipe outside of property boundary but only serving one unit) are
public sewer.

• Connection to the public sewer must be by one of the following methods:

1 Pre formed junction
.

2 Saddle Connection
.

3 Existing Manhole
.

4 New Manhole
.

1 Pre formed junction
.

o Junctions were used where two drain lines
meet such as a branch line from a soil vent
pipe connecting into the main line drain
running parallel with the property.

o Connections to the public sewer should
generally be made using oblique junctions.

o A junction is inserted into the line of the
public sewer after a section of the existing
pipework has been cut out and removed.

o Openings in the existing sewer must be
squarely and accurately cut using a pipe
cutter or disc saw.

o The installed fitting should be in good
alignment with the existing sewer.

o Oblique junctions shall be the same oblique
material as the existing public sewer and junctions
be placed in the direction of flow

1 Pre formed junction
.

2 Saddle Connection
.

o Saddles are a way of connecting to an existing
pipe by actually breaking into the pipe
through circular hole.

o A single hole in the Public Sewer must be
made.

o All saddle connections must be core-drilled.

o It should be noted that forming openings
using circular cutting wheels weakens the
pipe and causes structural defects.

o Saddles shall be the same material as the
existing public sewer.

o The use of saddles to clay or concrete sewers
is acceptable where the public sewer
diameter is three increments larger than the
connection diameter.

o A short piece of pipe with a socket attached
shall then be inserted into the hole and
sealed with epoxy mortar.

2 Saddle Connection
.

3 Existing Manhole
.

o Most existing manholes will be either brick-
built or constructed from pre-cast concrete
(PCC) sections.

o Brick-built manholes typically have 215mm
thick brickwork, a heavy-duty percussion drill
is used.

o PCC manhole sections are usually only 50-
60mm thick, best to 'stitch-drill‘.

o With both of these types, it will be necessary
to break into the manhole to install a new
connection.

o A new connection is to be made on the left
hand side of the chamber to collect from the
soon to be installed pipework that will
connect to a new gully or similar.

o A hole needs to be made through the
brickwork to allow the pipe into the chamber.

o Connections should be made at soffit level by
cutting brickwork or concrete and inserting a
stub pipe.

3 Existing Manhole
.

o This is not the preferred method of
connection. The existing manhole may not
be able to accommodate the new
connection.

o If the existing manhole is found to be
unsuitable for connection then the
connection proposals will have to be
revised.

o If the manhole is suitable, the new pipe
shall be connected in such a manner that
the soffit levels of the existing and new
pipes are the same.

4 Manhole
.

o Manholes should be
constructed where there is a
change of direction and/or a
change of gradient, or where
access is required for
maintenance purposes.

o If the connection is to serve 4
or more domestic properties
you will be required to provide
a new manhole.

o The diameter or size of a
manhole chamber should
provide sufficient access for
maintenance

o The new connecting pipe work
must meet the main channel
at pipe soffit to soffit level.



EXISTING
MANHOLE

NEW MANHOLE

MACHINERIES/EQUIPMENT

Major
machinery/equipment for
this scope of work shall
include:-
❖ Excavator
❖ Backhoe
❖ Plate compactor
❖ Water Pump

Installation and Laying of Pipe for Sewerage
Reticulation Works

Step 1 ; - Mobilize required resources to carry out
Preliminaries works in accordance to the project
requirement.
Step 2 ;
Survey and - Contractor shall ensure that materials
Setting Out mobilized at site shall as per approved.

- Check and ensure that relevant materials
delivered are conforming to specification.

- Materials shall be stock piled and stored
properly.

- Location of manhole and sewer route
alignment shall be marking and set out
by using spray paint or cement.

- Reduced level for excavation work shall
be set out by placing Y16 steel bar or
timber peg, coloured in red and
embedded 300mm into ground.

Installation and Laying of Pipe for Sewerage
Reticulation Works (Cont’d)

Step 3 ; - The excavation of sewer route alignment
Excavation shall be in straight line according to the
Work setting out given by surveyor.

- Width, depth and level shall be
depending on Construction Drawing.

- The excavation will be open cut method
and the gradient of open cut slope is 70
degree maximum.

- Prevent/ protect any adjacent existing
structure or other underground services
against damages

- Dewatering shall be carried out in case a
water level rising up into an excavated
trench. Open trench shall be dry at all
time prior to proceed with VCP pipes
installation.

Installation and Laying of Pipe for Sewerage
Reticulation Works (Cont’d)

Step 4 ; - Lay of bedding (crusher run, sand, etc.
Installation of - After completion of bedding, the VCP
Vitrified Clay
Pipe (VCP) pipes installation shall carried out
accordingly to the manufacturer
Step 5 instruction.
Installation of - The gradient of pipe installation shall
Precast Sewer follow accordingly as indicated on the
Manhole construction drawing layout

- Once the excavation work for manhole
complete and deemed satisfactory, the
base of manhole shall be concrete
accordingly.

- As a manhole base cured, precast
manhole shall be carefully erected to
concreted base by using appropriate
tools and machinery

- The depth and invert level of manhole
shall be well monitored accordingly

Installation and Laying of Pipe for Sewerage
Reticulation Works (Cont’d)

Step 6 ; - Material harmful to the pipelines shall
Backfilling and not be used for backfilling.
Compaction
- The filing of the two side of the pipelines
Step 7 should be carried out simultaneously.
Testing
- There shall be at least 300mm of cover
the pipelines before plate compactor can
commence.

- All necessary testing including CCTV test,
flushing and sterling or flow test shall be
done by the specialist once the external
sewerage pipelines completed.

- The testing shall meet the S.O and
relevant Authority satisfaction and
approval.

- Any defect to reticulation system shall to
make good and leave in perfect order

❑ TESTING OF SEWERLINE

• All newly-laid sewer, including manholes, inspection chambers and the like,
should be tested for water-tightness

• A test is applied in once a section of drainage is completed, although the
contractor/pipe-layer will normally undertake a test prior to the official
inspection or during actual construction to ensure the drainage will pass

• There are two basic tests;

• These types of sewer inspections tend to be a more cost-effective way to
pinpoint the location of sewer and pipe blockages without needing to
conduct more invasive methods like digging or removing walls or flooring to
gain access to plumbing.

1 Flow Test / Water Test with

. Ping Pong ball rolling

2 CCTV Test
.

Water Test

• A water test is more useful in identifying any
leaks or bad joints that are causing the pipeline
to fail the test.

• A water test will only normally be required to
verify a failed air test or to test manholes or
inspection chambers.

• Failure during an air test is NOT sufficient reason
to condemn a pipeline.

• If an air test indicates a leak in the system, a
water test must be then undertaken to verify and
quantify the problem.

• A water test can take 2 hours or more to
establish, and is less convenient as an ongoing
check for water-tightness of newly installed
pipework.

• Water test is carried out for pipe line and a
Manhole or Inspection Chamber.

Water Test

• The procedure of water test for pipeline;

1.Water is added to the pipeline (via a hose) up to the required head level
in the vertical pipe and the pipeline visually inspected for leaks.

2.The water is left to stand for at least 120 minutes, to allow for
displacement of trapped air and any absorption by the pipe, before being
topped up to exactly the required level.

3.The set-up is then monitored for a period of 30 minutes, during which
the water level of the head is topped-up as required at regular intervals
and the quantity of water added is recorded.

4.After 30 minutes the total quantity of water added to the vertical pipe
during the monitoring period is calculated and can be checked against
the table opposite - read off the figure given for maximum acceptable
loss for the diameter of pipe under consideration, and multiply that by
the length of pipeline being tested.

5.The measured quantity must be LESS than the calculated quantity for the
pipeline to pass the test.

Water Test

• The procedure of water test for manhole or inspection
chamber;
1.Manholes and Inspection Chambers are tested in a manner
similar to pipeline.
2.All inlets and the outlet of the MH/IC are stoppered and the
chamber filled with water to within 300mm of the soffit.
3.After a period of acclimatisation (60-120 minutes), the water
level in the chamber is visually monitored for 30 minutes.
4.Acceptable water loss can be calculated on the same basis as
that for pipework, although most tests look for a water loss
of less than 25mm over a 10 minute period.

CCTV Test

• Closed Circuit Television Video (CTTV) sewer
inspection refers to the process of using a camera
to see inside of pipelines, sewer lines, or
drainage.

• CCTV help to find the exact cause of sewer
damage, including

❖ Pipe cracking

❖ Offset joint pipes

❖ Corrosion

❖ Poor installation or previous repair efforts

❖ Blockage

❖ Accidental puncturing

CCTV Test

• Once the cameras are inserted, we are able to see a precise picture of sewer
pipe's condition so that can detect any severe damages located inside

• Benefit CCTV Inspection
❖ Affordable
- Identify the most affordable repair solution possible
- Sometime, repairing the entire length of an underground sewer pipe is
unnecessary.
- Repairs can then be focused on the damaged section only, reducing the
cost – and the time
❖ Environmentally Friendly
- No digging involved
- Plants, shrubs, and other natural elements won't be affected in the
inspection process
❖ Identify Problems Quickly
- CCTV inspections can check the whole pipe
- Get expert advice on a solution for pipe and make a plan to fix faulty
pipework.

THANK YOU