DISTRIBUTION SYSTEM APPURTENANCES
The SPU water
distribution system includes a number of smaller appurtenances, such as valves,
hydrants, service lines, and meters. The paragraphs below summarize SPU's
inventory and replacement approach for each class of appurtenance. Distribution
System Valves. SPU's water distribution system includes more than 21,000
valves. More than 16,600 valves control the flow of water through the
distribution system, but other valves regulate pressure, bypass other facilities,
or allow air to escape the system. Most valves within the distribution system
are gate valves. The only significant modification to SPU's valves planned
since the 2001 Water System
Plan will be the valve
chamber replacement program that will replace existing chamber tops and access
maintenance holes with larger diameter tops and new access ladders. This
program will provide SPU maintenance staff with safer valve chamber access and
meet industry safety standards. SPU has an ongoing program to replace line
valves when they fail beyond repair, when no replacement parts are available,
or where the cost of repair exceeds the cost of replacement. The determination
of when a valve should be replaced instead of repaired is based on consultation
among SPU staff experts.Distribution System Service Connections. SPU maintains
approximately 180,000 service connections, 80 percent of which are ¾ -inch diameter
pipes. Almost 70 percent of service connections are copper, and 20 percent are
plastic. The remaining 10 percent are galvanized iron, ductile iron, and other
materials.
The most significant
change to SPU's service connections since 2001 is the initiation of a program
to proactively replace noncopper service connections with copper connections.
This program is intended to reduce the high leakage and failure rate
ofnon-copper service connections
and is expected to be complete by 2015. The most
appropriate assessment of the condition of SPU's service connections is their
leakage rate. In 2005, SPU's leakage
rate from its service connections was approximately 2.8 leaks per 1,000 service
connections. This is lower than the IWA's
target leakage rate of 3.75 leaks per 1,000 service connections for a well-run
utility. The current volume of leakage from SPU's service connections is
estimated between 2.8 to 4.0
million gallons per day (mgd), or between 15 to 22
gallons per day per service connection.
IWA's target leakage
volume is approximately 15 gallons per day per service connection. SPU's non-copper
service connections have leakage rates that are greater than 5 leaks per 1,000
service connections. By proactively replacing these non-copper service
connections with copper connections, SPU expects to reduce the service
connection leakage rate down to 1.5 leaks per 1,000 service connections, well
below the IWA target. For all other copper services, SPU's replacement program
is a 'run-to-failure' strategy, since the impacts of a failed copper service are
typically minor, and the services can be quickly replaced. Distribution System
Meters. Each service line is fitted with water meters used to determine
customer charges. Most of the meters (87 percent) are for residential
customers, and the remaining 13 percent are for commercial customers. Nearly 92
percent of SPU meters are small (3/4-inch and 1-inch). Since the 2001 Water
System Plan, the most significant change to distribution meters, other than
routine meter replacements and repairs, has been the installation of radio
frequency modules on difficult-to-read meters in the downtown area. Also, radio
frequency modules were installed in 2005 at a group of multifamily residential
meters to pilot-test a new technology to collect readings from a single
pole-mounted collector.
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2024 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.