Trying to figure out why my pump is being difficult, hoping for some tips on something I haven't tried yet. I have a SF80110-2 that came with our 18' x 54" round Intex Ultra pool purchased last summer. The pump has run well for the first season but I noticed it starting to not perform as well lately. We were advised to run the pump for a min of 4 hrs. a day and had done so with no issues. Towards the end of the season last fall it started to run for only an hour or so and then very little output back to the pool. The motor would run but the output was very poor so I ended up just turning it off when it slowed down. For the start of the new season as recommended I changed the filter sand with new, backwashed and rinsed twice for good measure. Same performance as end of last season, short runtime to little output. Cleaned basket, barely anything there. What am I missing? Help please!