I got a new 350lb sand filter ( I had a 75lb before) this year. The pool shop said that with the filter being so big I need to take all the sand out of the filter for winter. Is this true? I backwashed the filter and drained the pool down to the return and disconected all the pvc lines and the pump and took them inside for the winter. I set the valve on the filter to winter and took the drain plug off and drained the filter ( this is how I have done the last 19 years with my other filter) Is this good or do I need to take the sand out? Also does it hurt my pool or liner to not to cover the pool for the winter? Thanks for the help.