In this model, leakages are equal in quantity to injections of spending from outside the flow at the equilibrium aggregate output.
The model is best viewed as a circular flow between national income, output, consumption, and factor payments.
Savings, taxes, and imports are "leaked" out of the main flow, reducing the money available in the rest of the economy.
Imported goods are one way this may happen, transferring money earned in the country to another one.
Large companies have factories or production facilities in less developed countries, these factories create wealth for the company which is then not transferred to the economy of the host country and instead to that of the corporation involved.