See if you can buy -- and transport -- 100# containers of cal hypo locally. You're looking for prices of $2.75/lb or less.

You could also see what it will cost to have Leslies or one of the other online consumer chemical companies deliver it to you.

But . . . you'll need to comfortable monitoring your chemistry with a K2006 to pursue this. I've successfully used cal hypo on multiple occasions in large commercial pools, without having problems with calcium build up or pH. But it will be an off-label application method.

Also, you will have to be able to periodically backwash, or else open and wash out, your filter to use this method.