Thanks Janet. From your first answer it sounded like you had some other suggestions before going the DE route? You had also asked for pump & filter info:
Hayward 1.5 HP Hayward HP Power-Flo economy pump for above ground pools
Filter is a W. Cooper Industries Ranger Series Sand Filter Model RS1815 & the multiport valve model number is TM-12-L. (needs new pressure gauge)
From the paperwork I have the valve size on this model is 1 1/2", tank diameter is 18" & the turnover rate is 12,760 gallons per 8 hours. My pool has 11,000 gallons of water.