Page 220 - Water Loss Control

Contr olling Appar ent Losses—Customer Meter Inaccuracy 193

side of the meter’s measuring element. A tagging saddle, brass nipple, and ball or gate
valve should be installed on top of the spool piece. These devices are used during the
field-testing of the meter. Most compound and fire service meters have test plugs built
into the meter casings. Many 4- and 6-in sized meters typically have 2-in test plugs,
while 8-in and larger meters often have 3-in test plugs. Prior to installing the meters the
test plugs should be removed and replaced with brass nipples and either ball or gate
valves to facilitate field-testing of the meters. The ball or gate valve is needed to safely
relieve pressure from the meter before opening the main casing. There have been
numerous accidents where the test plug has blown out during removal when the main
gate valves were leaking and the meter was under pressure. Use great caution as meters
can encounter working pressures of well over 100 psi, which can impart destructive
forces if weak or corroded fittings fail and are expelled.
Nearly all turbine meters manufactured prior to 1992 offered no test outlet in the
meter body and required a separate spool piece and test nipple installation downstream
of the meter. When test plugs are fitted in the meter bodies, a separate test tap is not
needed. Test outlets typically range in size from 1 to 2 in, depending on various meter
sizes. Additionally, some commercially available fire line meter assemblies and com-
pound meters can be provided with a test riser outlet assembly with a locking ball valve
and fire hose coupling for proper testing. See Figs 12.10, 12.11, and 12.12 for installation
recommendations for compound, Turbo (turbine), and fire line meters.

The Customer Meter Accuracy Testing Process
In conducting meter accuracy testing, it is of critical importance that personnel assigned
to perform the tests are properly trained and have the appropriate test equipment.
Meter testers are often designated as skilled field specialists or technicians in work
specifications, and training should be of sufficient caliber to reflect this skilled trade.
Appropriate techniques and procedures should be followed when using test equip-
ment. The consequences of discharging large volumes of water at high flow rates must
be understood, appreciated, and considered specifically for each test. Improper use of
the equipment may be harmful to testing personnel, the meter, the surrounding area,
and the general public. The meter pit must have adequate space in which personnel can
operate safely. In the United States, safety requirements published by the Occupational
Safety and Health Administration (OSHA) should be followed.
Prior to running any test, determine the make, model, and manufacturer of the meter
in question and document this data on the meter test sheet as shown in Fig 12.13.
In planning on-site testing of large meters, the technician must assess a number of
factors that are critical in conducting a safe and accurate meter test. A checklist of the
steps of the large meter testing process is given in Table 12.9. The technician must care-
fully identify the impacts of the large volume of water that must be passed through the
meter tester to run the test. One thousand gpm is not an uncommon rate to test the larg-
est of meters. Suddenly extracting such a high rate of flow from the water distribution
system could reduce the supply pressure in the local water supply grid and/or release
debris in the service line to the customer or adjoining water mains. The technician must
also assess where to safely discharge the large volume of flow that is passed through the
meter during the testing process. An uncontrolled discharge can cause considerable
damage to landscapes or private property, or create a safety hazard to vehicular or
pedestrian traffic. Discharge water must be safely disposed of in a manner than does
not cause any damage or violate any environmental regulations.