I have a large in ground Spa Pack that uses a 1.5hp pump for recirculation and filtering and a 2 hp pump for for the 8 jets that it has.It has 2 vent lines sticking out of the ground about 18inches that make a gurgling noise when the pump is running. When I turn the pump on that controls the jets they will start up and have plenty of bubbles and agitation but with in a minute or two the bubbles and agitaion stop. The pump continues to run but the strainer basket in the front of the pump will empty and try to refill. After another minute the strainer will fill and the jets will go back to work again for another minute or two and the basket will empty again and finally refill and go back to work again for 2 minutes. The jets don't seem to be clogged and this pump does not have any filters to be clogged. The impeller seems to be in good shape and the veins are not clogged with something. The distance between where the pump is at and where the hot tub is at is about 20yards. When the hot tub was new it seemed to work fine but there has been an ongoing issues with the jets that has something to do with this probably. Any thoughts or ideas short of filling it in with dirt and making a planter out of it...