Supplementary Material 2.3

Chapter 2 – Why WPM?


Surge Analysis and the Wave Plan Method

Supplementary Material: Example Problems and Solutions

Chapter 2 – Problem 2.3

2.3 Select all applicable answers to the following questions.

a. Almost all drinking water distribution networks in developed countries experience significant amounts of water loss through leakages at pipe joints and hairline cracks in pipelines. The reasons for pipe leakages and hairline cracks could be:

i. Poor workmanship at the time of installation.
ii. Aging infrastructure resulting in natural deterioration of pipe joints.
iii. Fatigue loading associated with the alternate cycles of extreme high and low pressures resulting from
surge events (e.g., pump operation where pumps are turned on/off, pump trip conditions, hydrant testing, valve operation, slam pressures, including check valve slam pressures and air valve slam pressures).
iv. Pipe aging alone is responsible for pipe leakages.
v. Aging pipes are more susceptible to developing hairline cracks and leakages when subjected to fatigue loading associated with surge events.
vi. Corrosion.

b. What should customers to do when their local water utility or health official issues a “boil water” advisory/notice?

i. Boil a gallon of water in a kettle and watch the dancing bubbles
ii. Do not drink water from the kitchen faucet (or any other tap) without boiling it first
iii. It is acceptable to drink tap water if it is passed through an ordinary household filter
iv. Drink bottled water from reliable sources

c. What is(are) the difference(s) between a boil water advisory and a do not use notice?

i. Both refer to the same “do not drink water from the faucet” advisory
ii. Switch to bottled water temporarily in the case of a boil water advisory but permanently in the case of a do not use notice
iii. When under a boil water advisory it is acceptable to use tap water for cooking (where the water reaches the boiling point at some point during cooking) but with do not use notice, tap water is not fit for cooking.
iv. Boil water advisories are issued in cases of microbial contamination while do not use notices are given in cases of chemical contamination
v. Do not drink water from a kitchen faucet (or any other tap) without boiling it as a precautionary measure in both cases
vi. It is acceptable to drink tap water if it passes through ordinary household filter in both cases

d. Potential sources of contamination of treated water within the distribution network include:

i. We do not understand the contamination process well enough to identify the sources of contamination
ii. Absence or disappearance of residual disinfectant leading to growth of harmful bacteria within the pipelines
iii. Low-pressure conditions resulting from surge events (such as pump trips, rapid opening of hydrant, etc.) allowing contaminated groundwater to flow into the distribution network through existing pipeline cracks or leaky joints
iv. Insufficient flushing of pipelines after a repair event
v. Water tanks with large quantities of stagnant water
vi. Intentional injection of contaminants
vii. Large surge tanks where the water remains stagnant for several days

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