PDFWAC 173-173-110
What are the installation requirements for meters on pressure systems?
Meters required under this rule shall meet the following installation requirements:
(1) The meter shall be installed in accordance with manufacturer specifications.
(2) There shall be a full pipe of water at all times when water is being withdrawn.
(3) The meter shall not be installed in a manner that creates an uneven velocity profile. Straight sections of pipe before and after the meter, straightening vanes or other flow conditioning devices shall be used to provide even flow through the meter as necessary.