If air bubbles are constantly present in the strainer, what is the most likely cause?

The presence of constant air bubbles in the strainer is most commonly attributed to a faulty gasket. A gasket forms a seal between components, such as the strainer and the pump. If the gasket is damaged, worn out, or improperly installed, it can allow air to be drawn into the system from the atmosphere. This influx of air will lead to the formation of bubbles in the strainer as the system attempts to draw in water for circulation.

While partial blockages in the line could also cause turbulent flow, leading to the formation of some air bubbles, they typically wouldn’t result in a constant presence of bubbles like a faulty gasket would. The other options, such as a blowfish stuck in the inlet or an oversized pump, are less common situations and would not generally produce a consistent presence of air bubbles. Understanding the sealing and suction dynamics helps clarify why a compromised gasket is the most likely cause of this issue.