We just purchased a new spa about 3 months ago. A few weeks ago, we have noticed that the dual speed pump, when on the second speed and the air valve open, the pump will surge. Is this normal or is there a problem? If a problem, what could it be? The filter is clean, the gate valves are open. The dealer says it is a dirty filter, but our filter is clean and is cleaned weekly.

Based on this post and your other one regarding the spa light, you really need to have your dealer (hopefully he's cooperative) to check this thing out. Something's not right.

Pump surging (where it sounds and acts as if it's sucking air and water alternatively) isn't a good thing and neither is that with the light fixture tripping the breaker.

You didn't mention the spa brand or model. That sometimes helps.