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Zhi Qing

                                         William Lai S10177395H

                                         Ng Sze Wei S10180575H                                                                                                                                   

















This report investigates
various types of system in Singapore. Mainly the potable water supply system,
sanitary plumbing and drainage system, basement carpark mechanical ventilation
system and air-conditioning system. This report will provide a detailed
explanation of the purpose of the various components that can be found in the
systems that was mentioned. Deeper understanding about the systems and the
components will provide fundamental knowledge which can be used for specific
situations such as the replacement of the buildings sanitary pipes. 



of Contents





1.     Introduction                                                                                          


2.     Potable
water supply system                                                                 


Pub stop valve chamber                                                                  


          2.2 Water storage tank

2.2.1 High-level storage tank

2.2.2 Low-level storage tank                                                              


          2.3 Master metre and Sub metre


          2.4 Auto pneumatic system


Sanitary plumbing and drainage system


3.1 Discharge pipe and
Discharge stack


3.2 U-Trap


3.3 Ventilating pipe
and Ventilating stack


3.4 Inspection Chamber


3.5 Sewage ejection


3.6 Grease Trap


Mechanical ventilation system for a basement


          4.1 Supply system

4.1.1 Supply fan

4.1.2 Jet thrust fan

4.1.3 Supply intake


          4.2 Exhaust system

4.2.1 Exhaust fan

4.2.2 Exhaust

4.2.3 Low level exhaust grille


          4.3 CO sensor





Air-conditioning system


5.1 Condensing unit


5.2 DX Fan coil unit of air cooled split unit


5.3 Chilled water fan coil unit


5.4 Supply air duct

Flexible duct

Rectangular duct


5.5 Supply air outlet


5.6 Cooling tower





Appendix A:
Potable water supply system                                                        


Appendix B: Sanitary
plumbing and drainage system


Appendix C: Mechanical
ventilation for a basement carpark


Appendix D:
Air-conditioning system                                                               











1.    Introduction

The purpose of this report is to discuss in detailed about the various
systems that are around us, specifically the potable water supply systems,
sanitary plumbing and drainage system, basement carpark mechanical ventilation
systems and air-conditioning system. By examining the various systems in
Singapore and with the aid of internet sites on the various systems, this
report provides a clear understanding about the systems.


Potable water supply system

Singapore have five potable water sources; local water catchment,
imported water, NEWater, desalinated water and also ground water. Water
obtained from sources such as local water catchment and ground water have to be
processed before it becomes potable water.


Potable water is clean drinkable water that are bacterially, chemically
and physically pure. This means that they are free from harmful bacteria,
harmful chemical, colourless, free from suspended matter and pleasant to taste.


In Singapore, the potable water supply system is managed by the Public
Utilities Board (PUB) who regulates the use and consumption of potable water.
All buildings in Singapore is able to obtain their potable water supply from
the PUB water mains.


2.1  PUB stop valve

PUB stop valve chamber is normally located between the service pipe
that connects to the water mains through a ferrule and the master meter. The
stop valve is provided so that PUB is able to shut of the water supply system
when needed. Situations where PUB needs to shut of the water supply system to
the building includes repair works of the buildings water supply pipes. In
situations when the water starts to backflow, the stop valve can be closed to
ensure that the water does not enter the water mains. This is to ensure that
that water in the water mains does not gets contaminated by the water that


2.2  Water storage tank

Water storage tank of a water supply system have three purposes.
Firstly, by using a water storage tank, it helps to prevent against possible
interruption of water supply. Secondly, it reduces the maximum rate of demand
on the water mains. Thirdly, it limits the pressure acting on the distributing
pipes to bearable limits and also on the appliances to reduce noise, water
usage and wear and tear on appliances. Water storage tank is located at
different heights depending on the purpose and the height of the building that
it serves.


High level storage tank

As the name suggest, the high-level storage tank (Fig.1) is located at
high levels of the building. It is used differently depending on the height of
the building. For example, it can be used for mode 2 application. For buildings
with highest appliances between 25 and 37 metres above mean sea level, its main
purpose is to supply water to those level which have finished appliances
located between 25 and 37 metres above mean sea level of the building. This is
to ensure that those level which have finished appliances located between 25
and 37 metres above mean sea level of the building is able to receive water
with adequate amount of pressure as the mains pressure might not be sufficient
for those level during peak times. Being able to provide water for a 24-hours
duration is required for this application of the high-level storage tank.



Low level storage tank

Similarly, as the name suggest, the low-level storage tank(Fig.2) is
located at low levels of the building. It can be used for different modes
depending on the height of the building. For example, it can be used for mode 3
applications. For buildings with highest fittings above 37m mean sea level, low
level storage tank is used to connect to the water mains and the duplicate
pump. Its main purpose in this application is to store water before it is
connected to the duplicate transfer pump and transfer the water up to a
high-level storage tank.


2.3 Master metre and sub

A master (Fig 4) and sub-metre(Fig.5) scheme is applicable for
multi-unit residential, commercial and industrial premises. Under the scheme,
water is supplies to the multi-unit premises through a master metre which
registers the total volume of water used in the premises. The master metre account
holder will have to pay for the water charges based on the difference between
the registration of the master metre and all the sub-metres, including
leakages. For instances in a shopping mall, the owner of the shopping mall will
be keen in master metre rather than the sub metre and vice versa for the
sub-tenants of the shopping mall. Some areas a sub-metre will be used for can
be beverage stores which require potable water to run the business.


      2.4 Auto-pneumatic system

Auto pneumatic system(Fig.3) is a
system that uses compressed air to create pressure in an air tank which when
needed, will provide pressure in the water pipes to ensure appliances is able
to receive adequate amount of pressure. The system main component would be an
air tank with a diaphragm in it to prevent contact of the water with air in the
tank. It initially charges the air tank with air through an air charging valve
located at the top of the air tank. This system uses pressure switches which
are electrically linked to a pump starter to turn the pump on when the pressure
in the air tank hits its pre-set minimum. The pump will pump in water from a
storage tank into the air tank, the entry of water will push against the
diaphragm which compresses the air above the diaphragm. This creates pressure
in the air tank. When the pressure hits its pre-set maximin, the pressure
switch will switch off the pump. Only when a tap or appliance is being use, a
valve will be opened allowing the pressure air in the air tank to force the water
out from the air tank into the pipe. When air pressure in the air tank hits the
pre-set minimum, the pressure switch will turn on the pump and repeat the whole
process again.


Sanitary plumbing and drainage system

Sanitary plumbing and drainage
system in a building is crucial as it carries wastewater from the building and
into the sewage system. Sanitary plumbing system refers to above ground
installation and sanitary drainage system refers to underground installation.
In Singapore, the Ministry of the Environment and Water Resources (MEWR) is the
authority having jurisdiction over plumbing and sanitary drainage systems.


3.1  Discharge
pipe and discharge stack

Discharge pipes(Fig.6) are pipes
which conveys the discharges from a sanitary appliance or a floor trap. A
discharge stack is thus a main vertical discharge pipe that all the other
discharge pipe will connect to. A discharge stack experiences air pressure
fluctuation when wastewater is discharged from the plumbing system. It is thus
important to keep the air fluctuation within limits to prevent loss of water



3.2  U-trap

U-trap are basically traps that
comes with a u-tube for holding a column of water to prevent entry of foul air
from the drainage system into the building and should be accessible for
cleaning. Common trap designs include P trap(Fig.8), Integral trap, S trap(Fig.7)
and bottle trap(Fig.9). Integral traps are installed together with the
appliances, common appliance to have an integral trap would be a water closet. P
and S trap are commonly used for floor traps and bath tubs while bottle traps
are commonly used for wash basins and sinks. Comparing P trap and S trap, P
trap is preferred over the S trap as P trap is less likely to lose its water
seal through siphonage. 


3.3 Ventilating pipes and ventilating stack

Ventilating pipes(Fig.10) are pipes
provided to limit the pressure fluctuations within any sanitary plumbing system
while ventilating stack is a main vertical ventilating pipe which the other
ventilating pipes connects too. Ventilating pipes are normally used together
with ventilating stack in a fully ventilated system while ventilating stack is
used independently without ventilating pipes in a ventilated stack system.


3.4 Inspection chamber

Inspection chamber are chambers that provide access to drains for
inspection, testing ang clearing of blockages. From the inspection chamber, one
is able to see the main drain line that connects the inspection chamber to the
others and the branch drain line that connects to the main drain line.
Inspection chamber are located within a distance of 50m and inspection chambers
are needed at points where blockages are likely to occur. These points include
a change of junction, a change of direction, change of drain-line gradient,
change of pipe diameter or a change of pipe material. Due to safety purposes,
the inspection chamber is covered with a cover(Fig.11) at all times to prevent
accidents from happening. The first inspection should also be ventilated except
when there is a ventilating stack or where there is a provision of ventilating
stack as it would cause odour nuisance to the surroundings.


3.5 Sewage ejector system

There are many types of sewage ejector system available but the most
commonly used sewage ejector(Fig.12) in Singapore is the ejector pump system. A
sewage ejector is needed for appliances with dischargers located below the
public sewer invert level as they are not able to rely on gravity to discharge
into the inspection chamber. The main components of the ejector pump system are
the collection chamber, duty and standby pumps, fluid level controllers, control
panel, pipework and pipe fittings. The collection chamber is used to hole the
sewage and wastewater of the appliances and when the fluid level reaches a
pre-set maximum, the fluid controller will start up to pump the fluids into the
inspection chamber till the pre-set minimum is reached. All these can be
controlled by a control panel. In a sewage ejector pump system, a centrifugal
pump system is normally used due to its ability to lift a large volume of
liquid at a greater speed then the other types of pumps and it thus very
suitable to be used for this purpose.


 3.6 Grease trap   

Grease trap(Fig.13) is a type of that is required for eating
establishments to prevent the discharge of oils, fat and grease directly into
the sewerage system. As when grease is hot or contained in hot water, it is in
the form of an emulsion and if it is allowed to flow into the drains, it will
cool and adhere to the sides of the pipes. It is thus able to clogged up the pipes
if allowed to do so. The principle of operation of the grease trap is thus that
of congealing. By cooling grease in a large volume of water, it solidifies the
grease and allows it to float on the water surface. The grease that floats on
the surface will then be removed from the trap periodically.


Mechanical ventilation for a basement carpark

Mechanical ventilation is important for areas where it is not
accessible to natural ventilation because without mechanical ventilation for
such areas, air quality will be poor and there will be discomfort due to the
lack of fresh air. For mechanical ventilation, it uses fans to create a desired
condition by bringing in fresh air into the carpark. As compared to natural
ventilation, mechanical ventilation allows more control over the air movement
as depending on the weather, the air flow created by natural ventilation
varies. The system is designed to provide constant or variable airflow rates as
required throughout the whole carpark. There are 3 types of mechanical ventilation
system, which are supply systems, exhaust system and combination of both.


      4.1 Supply system

In a supply system, outdoor air is delivered by a fan to the ventilated
space and room air allowed to exfiltrate through the openings. The outdoor
supply air can be treated as required using method like filtered. The slight
positive pressure in the ventilated space helps to ingress of air and dust or
smoke from the surrounding space. Examples of application that uses supply
system are internal staircase and ventilation of fire-fighting lobbies. For
basement carpark. Supply air shall be drawn directly from the exterior and its
intake not less than 5 from any exhaust discharge openings.


4.1.1 Supply fan

Supply fans(Fig.14) are designated to provide unrestricted airflow and
maximum weather protection. There are 2 types of supply fan which are the
centrifugal fans and the axial fans. For centrifugal fans, the air flow into
the impeller axially and is discharges radically into the volute of the casing.
It is more suitable for medium to low volume flow rate at medium to high
pressure. And for axial fans, they are used for high to medium flow rates at
medium flow rates at medium to low pressure. Their advantage are reduced size
and weight and the straight through airflow makes installation very compact.


      4.1.2 Jet thrust Fan

Jet thrust fan(Fig.19) is a fan that are suspended from the car park
ceiling replacing ductwork and mostly use in carpark. The function of the fan
has a similar function as the grilles in a traditional ducted system allowing
the control over the supply and exhaust air movement within the carpark.


      4.1.3 Supply Intake

Supply intake is defined as taking in fresh air to the surroundings.
Main supply intake grille(Fig.16) is one example of supply intake, where its
function is to take in fresh air for ventilation. The purpose of the grille it
to prevent any obstruction from failing the system.


      4.2 Exhaust System

In an exhaust ventilation system, fans are used to extract air from the
indoor space and discharge it outdoors. This creates a negative pressure in the
room. Outdoor air is then entering through the openings provided to replace the
extracted air. Examples of application include removing hot or polluted air
from kitchens, toilets and laboratories.



      4.2.1 Exhaust Fan

An exhaust fan system(Fig.15) provides a number of benefits, including
the purifying of air from pollution and excessive heat. As the fan’s motor
runs, the blades will start to turn. The rotation of the blades causes the hot
air in the room to be pulled towards the fan and sort of absorbed. This hot air
is released outside and in turn cooler and fresher air will start to fill the
room. This flow of current will also reduce stagnation of air and is especially
important and useful in rooms or areas that lack appropriate ventilation. In
exhaust fan, there are a few components that made up the fan. They are
silencers, vibration isolator, flexible duct and flexible connection. For
silencer, it is normally placed before and after the fan in the exhaust system.
Its main purpose is to control the noise level produced by the fan. Vibration
isolator is to isolate the whole fan system away from the supporting structure.
For flexible connections, it is installed between fan and metal ducts to reduce
transfer of fan or motor vibration to ductwork. Neoprene rubber or canvas
materials are used where it is installed loosely, in folds, so that they can
flex easily as equipment vibrates. And lastly for flexible duct, it is used for
final connection between metal duct and diffuser terminal and it is normally
reinforced, flexible and insulated.


      4.2.2 Exhaust

Exhaust which is known as extracting air from the indoor space and then
discharge it to the outdoor space. One example of exhaust is the main exhaust
grille(Fig.17) where it allows the air to flow out through the exhaust grille
after “using” the air.


      4.2.3 Low level exhaust

For low level exhaust grilles (Fig 20), the function is that it
extracts the exhaust air which are heavier than air from low level not
exceeding 650mm above the finished floor. It also allows dust particles pushed
from the operators breathing zone to be removed from the booth.


      4.3 CO sensor

The main function of CO sensor (Fig 18) is to control the speed of the
ventilation fan. During the times when the level of CO is high, the speed of
the ventilation fan can be increase so that the area is able to ventilate the
area faster. When CO level is low, the speed of the ventilation fans can be
kept at the minimum to ensure energy is used efficiently and a slightly
negative pressure is maintained


Air-conditioning system

Air conditioning system is installed and used to maintain a desired
indoor condition either for comfort, industrial process or maintaining quality
and life of stored product, energy will thus be transferred from or to the
space to compensate for the heat gain or loss due to internal or external


5.1  Condensing unit

A condensing unit(Fig.23) uses a condenser that provide a heat transfer
surface through which heat can pass from the hot refrigerant to the condensing


5.2  Direct Expansion
Fan coil unit of air cooled split unit system

Direct expansion fan coil unit is also known as DX fan coil unit(Fig.21).
it is a part of the direct expansions system which functions by evaporating and
condensing a refrigerant in a cycle. DX fan coil unit consist of an air cooling
evaporator and an evaporator fan. It operates by allowing room air to enter
into the system passing through a air filter, the room air then comes into
contact with the air cooling evaporator and cools the room air. The evaporator
fan then sends the cooled air out of the system, supplying the room with cooled


5.3  Chilled water fan
coil unit

In a chilled water fan coil unit(Fig.22), chilled water at a constant
temperature from a central refrigeration plant is supplied to individual
chilled water fan coil units serving the rooms. Through heat transfer, heat is
removed from the air and cooling it by passing it over the cooling coil the fan
coil unit in this system consists of a fan, a cooling coil and other


5.4  Supply air duct

Function of a supply air duct(Fig.24) is to supply air to rooms through
the end of the duct grills where it registers or diffusers are used. The AHU (Air
Handling Unit) consists of filter, cooling coil etc. When air passes through
the filter and then the cooling coil the air gets treated and it is now ready
for supply into the room. When this air has to be delivered into various rooms
then ducting is done.


      5.4.1 Flexible duct is used
to transport heated or cooled air from the unit into your home and vice versa
through the grilles or diffusers. It undergoes sagging and if it is not
properly supported, this will cause noises, leakage and the loss of air
velocity in an HVAC system. Flexible duct is made up of flexible plastic over a
metal wire coil to shape a tube. It can be normally found at shopping mall
where the ceiling is not really covered and shows al the pipes work.


       5.4.2 Rectangular duct

Rectangular duct is used to transport heated or cooled air from the
unit to homes and vice versa through the grilles or diffusers. However, it is
not like flexible duct where it doesn’t have a fixed shape. Rectangular duct
has a fixed shape and is made of mostly metal. 
It is also normally seen at shopping mall where both flexible duct and
rectangular duct can be found.


       5.5 Supply air outlet

The function of supply air outlet (Fig.25) is to supply air and
distribute the air inside the room. The air is supplied at low speed so that it
ca reduce minimal induction and mixing of the air. It is normally attached at
the ceiling.


       5.6 Cooling tower

The function of the cooling tower(Fig.26) is to cool the warm water
from the chiller condenser. The heat from the rooms in a building will be
transferred to chilled water, which is then transferred into the refrigerant,
then to the cooling water. The cooling tower is where heat transfer occurs. The
heat is then transferred to the atmosphere where the heat in the cooling water
is removed by letting it contact with the atmosphere. Plastic fillings are
arranged because it can increase the wetted surface of the water while it is
dropping, and the same time having more contact between the air passages and
the water.





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