2013 Water System Plan, Volume II - Seattle City Clerk's Office - City ...

Chapter 5 Water Infrastructure
5.6.4 Appurtenances
Pipeline appurtenances (line valves, access ports, blow-off/drains, and air release/air vacuum
valves) must be provided along the pipeline as needed to support the pipeline function and
operation. Appurtenance locations should be determined during design and consider conflicts
with other structures, vehicular traffic, and existing utilities. Appurtenance locations should
avoid areas most vulnerable to damage or vandalism.
5.6.4.1 Valves
When selecting a valve for a distribution main, pay close attention to the type of valve, whether
a bypass is required, clearance for future maintenance, and purpose of valve (sacrificial,
throttling, isolation). The types of valves used in the SPU water system are shown in Table 5-5.
For more information on valves, see Standard Specification 9-30.3.
Table 5-5
Valve Uses within SPU Water System
Use Type Function Size
(in inches)
Comments
Line Valve Gate, C509 resilient On/Off 4” – 12” Typically used for smaller line valves
Gate, C500 double On/Off 4” – 12” No longer commonly used
disc
Much larger sizes in system
Butterfly On/Off 4”-12” No longer commonly used
More head loss than others
Ball
On/Off 16”-84” Typically used for line valves
More head loss than others
On/Off,
throttle
4”-48” Costly
Low head loss
District Valve Gate On/Off 4”-12” In chamber, generally closed, locked
out
Backflow Prevention Check Valve Prevents 4’-12’ Only allows flow in one direction
backflow
Air Relief,
Air Vacuum,
Air Release
Stand Pipe, Air
Valve, Combo Air
Valve
Allows air
in and/or
our of pipe
2”-16” Air release allows trapped air to
escape pipeline and improve flow
characteristics
Air vacuum allows air into pipe to
prevent collapse during draining.
Pressure Regulating/
Pressure Relief Valve
Sacrificial/
Throttling
Control Valve
C500 Gate
C515 Gate
C509 Gate
Ball
Plug
Maintain
system
pressure
Limit
discharge
Limit
discharge
Limit
discharge
Limit
discharge
Limit
discharge
Largest likely future need is 8”
2”-16” Maintains a constant downstream
pressure
4”-8” Typically the “Throw away valve” in
double valve setup
4”-8” Typically the “Throw away valve” in
double valve setup
4”-8” Typically the “On/Off valve” in double
valve setup
4”-8” Long-term high head throttling valve
4”-8” Long-term high head throttling valve
SPU Design Standards and Guidelines
5-31