My pool suddenly started building back pressure and when it shuts off blows the skimmer basket off with water spewing and blows the sweep hose apart. I had a home warranty and they came out and replaced a piece of pipe right before the pump and that seemed to fix problems for a couple of days. Then it started doing it again and have to prime system daily. The home warranty repairman thinks the filter sand needs to be replaced which I will do but don’t think this will fix the air problem. He also found where the pipe on suctioning side comes out of ground and been reduced to 1 1/2 in and then back to 2 in but has been this way for years as I have had house for 5 years and no signs of new work being done when I bought it. He claims that the restriction can cause air bubbles but why would it work fine for years and then suddenly start. I feel it must be in one of valves or pump. What are your thoughts?