Water Meter Bypass Requirement

[jartgo]

Do you all know if there is a general or standard requirement for a bypass line on a domestic water meter of certain size or larger. That is, I see a lot of standard municipal details that require a bypass with locking valve on meter sizes of 1.5 inch and larger. However, I can't seem to locate a state or national regulation or rule that dictates that being the case. I guess I was wondering if there was a Fire/AWWA/Building code that dictates that requirement or whether or not it has just been customary and adopted by many. Any insight on the origination of the 1.5 inch and larger design would be appreciated. Thanks in advance.
I'm specifically interested in this issue as it relates to North Carolina, if anyone has specific experience there.

 

[hydrae]

Meters smaller than 1.5 inch are connected using coupling nuts, while the larger meters are connected using flanges.
Flanges take significantly longer to disassemble and reassemble, so that would be my assumption that is were the need for a bypass would kick in.
In systems I have been involved with, the bypasses started at 3" though. 3" is the size that would be installed inside a vault instead of a meter box

Hydrae

 

[bimr]

My understanding is the bypass is used on larger commercial water meters so that the meter can be repaired without shuting the water off. The bypass has nothing to do with the fire code.

Some water systems use the bypass on smaller 1.5-Inch lines, but it is more typical for bypasses to be use on 3-Inch or larger.