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