having problem's with water staying cloudy..Had a heavy load of kid's Friday.Water turn's cloudy after a hour of swimming..My number's were all in check.I was showing about 1 on CC.I went ahead & started shocking .Kept it going Friday&Sat.Recheck'd last night .Past overnight test this morning...Current # Fc=18,cc=0,ph=7.8,Alk=100,Cya of 30..Did had 18 0z of Stab. yesterday to bump it up.My pressure is great on filter.I backwash'd again this morning no change on pressure..Pressure run's around 10-12.Have never changed sand on system.System is 8 yrs old.Wondering about channeling.How can you tell???