Patent ID: 7331769

Claim:
A pumping system, comprising: a primary pump for pumping a fluid from an inlet out an outlet, said primary pump including a pumping chamber adapted to receive fluid from said inlet; a suction chamber disposed above said pumping chamber; a throttle opening between said pumping chamber and said suction chamber; a priming pump for drawing fluid into said suction chamber; a fluid path around said pumping chamber between said inlet and said suction chamber, said fluid path having a larger area than said throttle opening; and a flow restrictor selectively restricting flow of fluid from said fluid path to said suction chamber, said flow restrictor further selectively permitting flow of fluid from said suction chamber to said inlet during operation of said primary pump, the rate of said selectively permitted fluid flow from said suction chamber to said inlet being at least as great as the rate of flow of fluid through said throttle opening during primary pump operation.