I recently purchased a used DE filter. I had it chemically cleaned at the pool store, so it should be clean. The problem is that I have 3-4 inches of algoe on the bottom of the pool. I added the algaecide the pool store sold me, so I am assuming the algae is dead. When I hook up the vacuum hose and start the filter, the pressure of the filter goes up to 20 lbs within 10-15 minutes. I have to turn off the filter, do the "bumping" and turn the filter on again. Is there something I am doing wrong, or do I have to sit by the pool constantly because the pressure increases so quickly? I have a 24' round above ground pool and recharge the filter with 3 pounds of DE.
I have seen in other posts that measuring CYA is important. What is CYA and how do I measure it?