1. Not a problem. Replace the cartridge with a 5 micron polypropylene sediment filter. Cartridge size would be 2-1/2" x 10". 2. If sand in water is the issue, all you need is a sediment filter. However, this filter system is too small for effective filtering. I would suggest at least a 4.5" x 20" big blue sediment filter system. A CCMG backwashing system is even better. 3. Manufacturers speak of the superiority of one over the other, but they seem about the same.