Sun Shades and Evaporation Loss

Gasoline evaporation losses can be sizable from unsheltered aboveground tanks. A red gasoline storage tank exposed to direct sunlight may lose over 9 gallons of fuel a month. Gasoline tanks should be a reflective color such as white or aluminum, and be shielded from the sun with an overhead canopy unless already located in a shaded spot.

Note: To further reduce evaporation losses, use an approved pressure-vacuum relief valve, rather than a standard vented cap. When tank pressure rises, the pressure-relief valve opens, allowing only enough fuel vapor to escape to relieve excess pressure. When the tank cools or fuel is withdrawn, the vacuum-relief valve opens, allowing air into the tank to nearly equalize inside and outside (atmospheric) pressure -- which permits a free outflow for fast equipment refueling with gravity-discharge tanks.

[Note -- These are recommendations in Indiana, but may be required in some states for aboveground storage tanks - check with local authorities.]

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