Abstract: A liquid-gas bubble separator comrising a container having an inlet for a fluid which includes liquid and gas bubbles, an outlet and upstream and downstream vents. A filter element is provided in the container between the inlet and the outlet. The filter element permits the passage of the liquid and inhibits the passage of the gas bubbles. The filter element is between the upstream and downstream vents so that gas bubbles which do not pass through the filter element can be vented through the upstream vent, and any gas bubbles downstream of the filter element can be vented through the downstream vent. A bypass passage is provided around the filter element. A portion of the filtered fluid is recirculated through the bypass passage to prevent forward flow through the bypass passage when the filter element is clean, and such recirculating flow is terminated when the filter is clogged to a predetermined degree to thereby open the bypass passage for forward flow.