at the end of last season i was getting alot of sand in my pool. it was a good bit of sand in the far end. i have a 15x30 above ground pool 11,000 gallons. 

i also have not changed my sand in about 7years. i just took apart my sand filter got all the sand out. my laterals are fine no cracks or damage.

 my multiport valve needed a new spider gasket.  the gasket was destroyed.

what do you think is causing this?