I had the pool store come out again and they changed out the multi-port but it didn't help the problem. Next they started to change out the sand. I was told that down next to the laterals were quarter sized sand chunks-which were impeding the water flow. They wanted to know where I had been getting my chemicals. Thankfully, their shock has been cheap this year so I could say it was from their store. These chunks had formed within a few months. Anyone have any ideas why? I've only been using chlorine. The pump works great now, I just don't want this to happen again in a few months. Denise