A suction hose can never operate at higher than atmospheric pressure - ie vacuum is not a force in its own right, it is merely a lower pressure than the outside. In this case, atmospheric pressure.You are unlikely to create vacuum bubbles at this level of suction and even if you did, they'd disappear the moment they pass through the pump. Martin #1458 DMC Joe wrote: > Fuel under high pressure may be cavitating as it passes > the spring coils the resulting bubbles will increase pump noise.