hi i am new to this site and new owner of indoor inground pool we bought the house a year ago and ran the pool without any problems, then a couple months ago we noticed the heater wasnt heating , we had a pool guy come out and he replaced the capacitor the pressure switch and the thermostat. the heater would kick on for awhile but then shut off, someone said to turn the filter to the recirc position if it stays running the sand needs replaced, so i did that and it did stay running so i back flushed it and so far it is running but i think the sand needs replaced also so my question is how do i do it, i have the triton TR-60 i know it says to use 50 lbs of pea gravel and 275lbs of sand. i know to shut filter off open drain plug , take off octagon ring on top then what thanks for your help.