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WU017834 Rev. 05 July 2023 Wayne Fueling Systems | Dover Fueling Solutions 53
5.17 BALANCE VAPOR RECOVERY SYSTEM INSTALLATION REQUIREMENTS
5.17.1 Dynamic Back Pressure Testing
At initial installation, balance vapor recovery dispensers should have a dynamic back pressure test performed
at each nozzle to ensure there are no blockages in the vapor recovery system. The dispenser should be con-
nected to the underground and the hanging hardware (hoses, nozzles, breakaways, etc.) should be installed.
The following test methods or equivalent methods can be used:
● “ST-27 Gasoline Dispenser Facility Back Pressure.” Available from the California Bay Air Management
District at https://www.baaqmd.gov
.
● “TP201.4 Determination of Dynamic Pressure Performance of Vapor Recovery Systems of Dispensing
Facilities.” Available from the California Air Resources Board at https://ww2.arb.ca.gov/
.
Maximum allowable dynamic back pressure for an individual dispenser nozzle using either test procedure is
listed below:
60 cu. ft. per hr. < 0.35 in. of water
80 cu. ft. per hr. < 0.62 in. of water
NOTE! Very low numbers for back pressure results may indicate a leak in the system and it should be
checked.
5.17.1.1 Back Pressure System Check List
NOTE! Check test equipment for up-to-date calibration stickers. Normal use of rotameters and pressure
gauges necessitates yearly calibration; calibration is also required if this equipment has been dropped
or mishandled.
1. Check test equipment for leaks prior to use. Pressurize with nitrogen supply (plug nozzle end of the fill
pipe). Adjust nitrogen until 50% on pressure gauge is reached. Close off supply. A pressure decay
must not be more than 0.2 in. of water in five minutes.
2. If facility has a vapor pod (condensate pot), drain prior to testing.
3. Open dry break poppets.
4. Completely drain hoses and nozzles prior to test. A pulsating needle indicates fluid in the lines. Red-
rain if necessary.
5. The following information should be included on the field data sheet:
○ Facility address and ID
○ Pump number and grade ID
○ Nozzle make and model
○ Back pressure in inches of water
○ Nitrogen flow rate
6. If back pressure readings are very low (less than .02 @ 20 CFH; 0.18 @ 60 CFH; 0.4 @ 100 CFH):
a. Check test fixture for tight seal at nozzle entry point.
b. Check bellows and face seal for tears.
c. Check vapor piping for leaks.
7. If back pressure readings are high:
a. Check hoses and nozzle bellows are completely drained.
b. Check dry break is open. (If only allowed to have one dry break open during the test, try all.)
c. Check vapor pod.
d. Check vapor impact valve to be open.
e. Check piping under dispenser. Should be a minimum of 1 inch diameter piping and fitting.
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