JackVa11

Hi, a few days ago, we noticed that our # 1 pump began a rhythmic jet inconsistent pumping. It begins after using it for 15 minutes or so. You can hear the jet power decrease, then increase over and over every two seconds . 0nce it begins it stays in this state unless I turn it off for a minute which sometimes clears it up for a while, but it will return. We refilled the spa a few weeks ago , but it was fine for several uses. Any thoughts? The water level is fine and our #2 pump which is a two setting pump works fine. The filter area is clear and it's a new filter. thanks in advance j