Firstly, your Sand filter should be plumbed to sewer, rather than the storm water.
Sand filters are generally large round filters that use sand, or glass media to filter the water, whereas a cartridge filter resembles a tall cylinder and filters the water through a cartridge.
Cartridge filters are not backwashed like a sand filter and generally taken out and hosed down to clean them out. The cartridge filter element is eventually replaced as wear and tear take hold, whereas only the filter media (sand or glass) is replaced in a sand filter, to maintain the filtration efficiency.
Installation of a cartridge filter is important and with both cartridge and sand filters and it's really important to ensure that the size meets the requirements of the pool.
As long as they are installed and used correctly, cartridge filters can remove metals, sediment and some microorganisms from the water as efficiently as sand filters.
It's very important to know that cartridge filters don't like coagulants, and therefore any flocculants will most certainly block the filter quickly, causing you to have to regularly hose it down to unblock it in order for it to continue filtering.
TIP : Never use a coagulant or flocculant with a cartridge filter
