Water Supply Flashcards
1
Q
Potable Water must be…
A
- colourless
- free from suspended matter and harmful bacteria
- pleasant to taste.
2
Q
who regulates use & consumption of potable water in sg?
A
Public Utilities Board (PUB)
3
Q
Modes of Water Supply
A
Mode 1,2,3
4
Q
Mode 1 height of appliances
A
less than 25m above MSL
5
Q
Mode 2 height of appliances
A
25m - 75m above MSL
6
Q
Mode 3 height of appliances
A
above 37m
7
Q
RL =
A
MSL + 100
8
Q
Mode 1 mode of supply
A
direct supply to all appliances
9
Q
mode 2 method of supply
A
indirect supply through high level storage tank
10
Q
mode 3 method of supply
A
Indirect supply through low level and high level storage tanks with pumping equipment.
11
Q
Mode 1: how water goes up
A
- Appliances less than 25m above MSL are within reach of the mains pressure.
- The mains have a pressure head greater than 25m even at peak demand.
- Hence, water is available directly from the mains at all times.
12
Q
Mode 2: how water go up
A
- the mains pressure may be insufficient to supply water directly during peak times.
- But the mains pressure is sufficient during off-peak times in the evening.
- Hence, a high level water storage tank is required.
- If necessary, it is filled during the evening and supplies water to the building at all times.
- The high level water storage tank should be able to provide water for a 24-hour duration
13
Q
Mode 3: how water go
A
- The water from the mains will first fill up a low level storage tank.
- The low level storage tank serves as a reservoir &reduces demand on the mains pressure.
- The low level water tank should be located so that the inlet to it is below 37 m above MSL
- Where inlet to low level tank is between 25 and 30m above MSL, low level tank should be sized to be at least 1/5 of the daily water requirements.
- if inlet to low level tank is 30m & more above MSL, low level tank should be sized to be at least 1/3 of the daily water requirements.
- total storage capacity of the low level and the high level tanks should be equivalent to one day’s water requirements of the water service installations to be served by the tanks.
- From the low level tank, transfer pumps are used to deliver the water to a high
level tank. - The transfer pumps must be in duplicate, operating in duty cycles.
14
Q
Operation of Pumped Systems (Mode 3)
A
- The pumps are operated by level switches installed in the water storage tanks.
- Only one pump operates at any one time. The pumps operate in duty cycles.
- Level Switch B in the high level storage tank starts the pump when the water level
falls to a pre-set level. - Level Switch A stops the pump as the water reaches the pre-set high level.
- Level Switch C in the low level tank switches off the pump when the water level
drops to the pump suction connection. - This ensures that the pump does not run dry.
- Level switch C is the overriding switch. It stops the pump regardless of the signal
from level switch B.
15
Q
SEE NOTES, FIGURE 9
A
- level switch A
- Level switch B
- Level switch C
- Where pump starts and stops
- High Level Storage
- Low Level storage
- Electrical Connections
- Pump starter panel
- Duplicate transfer pumps
- PUB Supply
16
Q
Auto-Pneumatic System
A
- Water is pumped from the tank for storage in a pressurized air tank.
- Water is supplied from the air tank when required by the appliances.
- The check valve prevents water from flowing back into the water tank.
17
Q
Operation of Auto-Pneumatic System
A
- This system consists of a tank with a diaphragm that prevents contact of the water with air in the tank.
- The tank is initially charged with air through the air charging valve at the top.
- The system is provided with pressure switches which are electrically linked to the
pump starter. - When the air pressure in the tank is at the minimum, the pump starts to operate.
- The entry of water into the tank forces the diaphragm to rise and the air pressure
above the diaphragm increases. - When the maximum pressure is reached, a pressure switch will stop the pump.
- When a tap is opened, the air pressure above the diaphragm forces water from the tank to the pipe.
- When the air pressure in the tank reaches the minimum, the pressure switch will
signal the pump to start again and replaces the water drawn from the tank.
18
Q
GO NOTES LOOK AT FIG 11c
A
- Air Compressed by Water
- Appliance may be Shut or Open
- Pump Charging in Water
- Pressure Switch
- Air Tank
- Diaphragm
- Pump Working
- Check Valve Prevents Water Flow to Tank
- Pressure Switch
- Air Discharging Water to Appliances
- Air Pushing Out Water to Appliances
- To Appliances
19
Q
GO NOTES LOOK AT FIG 13b
A
- PUB Supply or from Low Level Storage
- Air Vent with Mosquito Netting
- Tight Fitting Cover
- Overflow Pipe with Mosquito Netting
- Warning Pipe with Mosquito Netting
- Float Valve
- Water Gauge
- Distributing Pipe
- Isolating Valve
- Washout Valve
- Washout Pipe with Mosquito Netting
20
Q
Water Efficiency Labelling Scheme
A
- Use of water products and fittings that are labeled under PUB’s Mandatory Water Efficiency Labeling Scheme (WELS)
- Install self-closing delayed-action taps at all wash basins.
- Install self-closing delayed-action shower taps at all shower points.
- Install constant flow regulators at all wash basin mixers, shower mixers and bib taps.
