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Old 03-09-2011, 04:47 PM   #27 (permalink)
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Originally Posted by Old Tele man View Post
...go to the GILBARCO VEEDER-ROOT website; they manufacture gas pump systems. Look under "fuel vapor recovery" for more info about how & why the tanks "suck" back excess fuel at the pump so as to not allow it to get into the air (especially used in California).'s what EPA has to say about it (text in yellow box):
Topping off the gas tank can result in your paying for gasoline that is fed back into the station's tanks because your gas tank is full. The gas nozzle automatically clicks off when your gas tank is full. In areas of ozone nonattainment, gas station pumps are equipped with vapor recovery systems that feed back gas vapors into their tanks to prevent vapors from escaping into the air and contributing to air pollution. Any additional gas you try to pump into your tank may be drawn into the vapor line and fed back into the stationís storage tanks.
So (1) the vapor is fed back into the station's storage tanks, regardless of much gas you get and (2) any gas you pump into your tank may also be drawn into the station's storage tanks. I don't quite get why it would only be "additional" gas. I wonder at what point this would happen, after the 1st click? the 2nd click? from the time you first put the nozzle in the tank?

If there is no difference at any time, then it doesn't matter how much the tank is filled up. If it's only when the gas reaches a certain level, then this depends on where that level might be.

Interesting, the stations might be fined a nominal amount if the pumps are found to provide less gas than paid for; however they are also encouraged to take gas back from the cars and to put it back in their storage tanks!
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