This document discusses hydrant flushing programs. It explains that flushing programs help maintain water quality by removing sediment, restoring chlorine residuals, and preventing issues like nitrification. The document outlines a four-step approach to flushing programs: determining if flushing is needed, planning the program, collecting data during flushing, and evaluating the results. It also describes different flushing methods like conventional, unidirectional, and continuous blow-off flushing and considerations for implementing an effective flushing program.

1. HYDRANT FLUSHING PROGRAMS
Brian Gongol
DJ Gongol & Associates, Inc.
September 16, 2015
Iowa AWWA Fall Short Course
DMACC / Ankeny, Iowa

2. Important note
 This presentation borrows heavily from an AWWA learning
module for small systems entitled "Distribution System
Operations and the Impact of a Flushing Program on Water
Quality"
 The AWWA module was funded by the EPA
 Much of the text and a limited number of illustrations are
taken from that presentation
 The layout/organization of the content and most of the
illustrations are original and are intended to improve upon
the original

3. What's the purpose of flushing?

4. Flushing is usually considered a corrective measure

5. Flushing is better seen as a tool to maintain water quality

6. Why flush?

7. Flush to address customer complaints

8. Flush to remove sediment and loose deposits

9. Flush to expel contaminants after a backflow incident

10. Flush to scour distribution lines

11. Flush to decrease water age in dead-end mains

12. Flush to restore chlorine residuals

13. Flush to prevent nitrification

14. Flush to respond to nitrification

15. A look at flushing programs

16. Who here has an active flushing program?

17. What triggers a round of flushing in your system?

18. A four-step flushing program

19. 1: Determine if flushing is appropriate

20. 2: Plan and manage flushing

21. 3: Collect data

22. 4: Evaluate and revise the program

23. Flushing isn't always appropriate

24. Ask these questions first

25. Do you use unfiltered surface water?

26. Do you use undisinfected ground water?

27. Do you have high iron and/or manganese?

28. Do you have positive results for coliform?

29. Do you have elevated heterotrophic plate counts?

30. Is your water chloraminated?

31. Has treatment changed in a way that could affect water quality?

32. Do your customers complain a lot?

33. Do parts of your system have low disinfectant residuals?

34. Are you aggressive about exercising valves, hydrants, and tanks?

35. Is your source water corrosive?

36. Does sediment accumulate in your storage facilities?

37. If you answered "Yes", flushing can help

38. To recap: Flushing helps in these cases
 Unfiltered surface water
 Undisinfected ground water
 High iron
 High manganese
 Coliform
 HPCs
 Chloramines
 Treatment changes
 Valve exercise
 Corrosive source water
 Sediment

39. If none of those apply, try something else

40. Five alternative options

41. Alternative 1: Source treatment

42. Alternative 2: Booster disinfection

43. Alternative 3: Valve exercise

44. Alternative 4: Pipe lining

45. Alternative 5: Storage tank elevation adjustment

46. But let's suppose flushing is appropriate

47. If you're going to flush, you need a plan

48. Plan your flushing with clear objectives

49. Objectives for water quality
 What are you trying to achieve?
 What has to improve?
 How much improvement is enough?

50. Objectives for cost
 It may not have reached the customers, but the water still
has value
 So does your time and labor

51. Plan for water quality
Flush with clean water behind you

52. Plan for hydraulic consequences

53. Plan for mechanical consequences

54. Determine flushing approach

55. Approach 1: Conventional

56. Approach 2: Unidirectional

57. Approach 3: Continuous blow-off

58. Three approaches in detail

59. Approach 1: Conventional flushing

60. Most common method

61. Requires minimal pre-design

62. Just keep opening hydrants
Open hydrants in the distribution system
until criteria are met

63. Criteria
 Disinfectant residual
 Discoloration
 Turbidity

64. Think ahead
 Don't draw poor-quality water into high-quality areas
 Most important for nitrification remediation

65. No isolation means low velocity

66. What can you expect from conventional flushing?

67. Restoration of disinfectant residual

68. Expulsion of some poor-quality water in some areas

69. But conventional flushing has shortfalls

70. Shortfall 1: Customer complaints

71. Shortfall 2: Wasted water

72. Shortfall 3: Improvements are minimal

73. Shortfall 4: Improvements are short-term

74. Shortfall 5: Risk of increased coliform incidents

75. Shortfall 6: Chlorinated water discharge

76. Is there a better way than conventional flushing?

77. Approach 2: Unidirectional flushing

78. Unidirectional flushing can be isolated in the distribution system

79. System-wide or as-needed

80. Velocity matters

81. Velocities 3 fps or greater
 Remove silt and sediment
 Reduce disinfectant demand

82. Velocities 5 fps or greater
 Promote scouring
 Remove biofilm
 Loosen deposits
 Reduce disinfectant demand

83. Velocities 12 fps or greater
Remove sand from inverted siphons

84. Pipe size, flow, and velocity
Size FPS GPM 400 gpm hydrants 1000 gpm hydrants
4" 6 250 1
6" 6 550 1
8" 6 950 2
12" 6 2,100 5 2
24" 6 8,300 8
36" 6 20,000 20

85. Other benefits of unidirectional flushing

86. Valves get operated
 Simultaneously flush and complete preventative
maintenance

87. Wastes less water than conventional flushing

88. Establishes baseline for future comparisons

89. Reduces troubleshooting

90. Unidirectional flushing illustrated

91. Unidirectional flushing illustrated

92. Unidirectional flushing illustrated

93. Unidirectional flushing illustrated

94. Unidirectional flushing illustrated

95. Unidirectional flushing illustrated

96. Unidirectional flushing illustrated

97. Unidirectional flushing illustrated

98. Think: Flush from the inside out

99. Guidelines for unidirectional flushing

100. Tell customers in advance

101. Reach out to high-need customers

102. High-need customers: Hospitals

103. High-need customers: Dialysis patients

104. High-need customers: Restaurants

105. High-need customers: Hotels and pools

106. Unidirectional flushing is for night owls
Avoids service disruptions

107. Start from the source and work outward

108. Use diffusers and hoses to avoid property damage

109. Water should move from flushed into un-flushed areas
That's what makes it uni-directional

110. Flush from larger into smaller mains
Think: Flushing from clean to dirty

111. Smaller mains shouldn't flush larger mains
 Not enough flow
 Not enough velocity

112. Keep pipe lengths short
 Use valves where appropriate
 Maximize velocity over short runs

113. Maintain pressure above 20 psi

114. Warning: Gate valves trap slugs of water
 If isolating with gate valves, re-open the valve before closing
the hydrant
 Removes slugs of water trapped behind valves

115. Get the most from unidirectional flushing
 Plan ahead
 Collect data
 Analyze the data
 Improve the next plan

116. Approach 3: Continuous blow-off

117. Used if you can't escape stagnation or circulation problems

118. Continuous blow-off is slow
Usually 1 fps or slower

119. Good for restoring and maintaining disinfectant residuals

120. Reduces water age

121. Usually results in significant water loss

122. Doesn't fix the problem at the source

123. Continuous blow-off illustrated

124. Mainly useful at small dead ends

125. Recap: Three options for flushing
 Conventional
 Unidirectional
 Continuous blow-off

126. If (appropriate) flushing has been planned and executed...

127. ...then for the love of Neptune, collect some data

128. Data key 1: Identify loops

129. Flush from large to small

130. Flush from source to periphery

131. Flush in loops that can be completed in one shift

132. Data key 2: Check your speed

133. Aim for 6 fps pipe velocities

134. Data key 3: Develop and document a sequence

135. Get specific
Detailed instructions for the order of
opening and closing valves and hydrants

136. Conduct a trial run

137. Be ready for the unforeseen, especially on a trial run

138. Flush during off-peak hours

139. Have a safety protocol in place

140. Collect data in action

141. Collect baseline data

142. Collect data during the flush

143. Collect data after the flush

144. So you've determined that flushing is appropriate...

145. ...and you've planned the flushing program...

146. ...and you've collected data on a trial run...

147. ...now, evaluate and revise

148. Did you meet the water-quality objectives?

149. How much did the flushing program cost?

150. How much did the flushing program save?

151. Did any bonus benefits result?

152. Did you encounter any unforeseen problems during or after?

153. Make it a habit
As with any good health practice,
do it again and again and again
Establish a baseline

154. A few nitty-gritty details

155. Do your training before you're in the field

156. How to flush a hydrant

157. Open and close slowly to prevent surges

158. A 1 fps velocity change can come
with a 50 to 60 psi pressure rise

159. Open hydrant valves completely
 Prevents water from discharging through the barrel drain
 Protects the hydrant support
 Preserves water quality if sampling from a partially-open
hydrant

160. Restrain your flow dissipators
 Limits property damage
 Protects workers

161. Discharge directly to sewers when possible

162. When sewers aren't available, redirect traffic
And use signage!

163. When is dechlorination appropriate?

164. Flushing time depends on the objective

165. Sample water frequently until objective is met

166. Common objectives
 Reduction in turbidity
 Reduction in color
 Increase in chlorine residual

167. The point of quality objectives
What's "good enough" determines
how much flushing is enough

168. Record flushing time to estimate water use

169. Hydrant safety

170. Use caution!

171. Flushing water has a lot of force

172. Water could contain rocks, bolts, and other objects

173. Check all attachments for tightness

174. Warn motorists and watch for traffic

175. Be cross-connection aware
When using hoses to discharge to sewers,
watch for cross-connection

176. Expect water hammer

177. Other people will notice

178. Coordinate with the fire department
 Promotes teamwork
 Kills two birds with one stone
 Offers a buffer with the public
 Fire departments are almost bulletproof in the public eye

179. Notify the public

180. They will think you're just wasting water

181. You are flushing to improve water quality

182. You are flushing to maintain the system

183. You are flushing to reduce chemical treatment

184. You are flushing to reduce chemical use in distribution

185. You are flushing to promote system hydraulics

186. You are flushing so they don't get sick

187. You are flushing to maintain fire protection

188. Resources
 AWWA Video – Unidirectional Flushing
 http://www.awwa.org/store/productdetail.aspx?
productid=7076
 AWWA Water Distribution Operator Training Handbook
 http://www.awwa.org/store/productdetail.aspx?
productid=36142344
 AWWA Water Distribution Systems Handbook
 http://www.awwa.org/store/productdetail.aspx?
productid=6435
 WRF Report: Guidance Manual for Maintaining Distribution System
Water Quality
 http://www.waterrf.org/Pages/Projects.aspx?PID=357

189. Questions?

190. Questions?
 Thank you for coming!

191. Thank you for your attention!
 Contact us anytime with
questions
 Brian Gongol
 DJ Gongol & Associates
 515-223-4144
 info@djgongol.com

192. References
 Primary text supplied by AWWA
 Flushing diagrams supplied by AWWA
 All other photos are original work by and copyright reserved
to Brian Gongol