I need to clean my cartridge filter for the first time and am wondering if there are any best practices I need to follow other than those stated in the manual. I do have a concern that I do not have inlet and return valves. The only valves available are those that direct the water to the pool or spa returns. In one position, the water goes to the pool, and in the other, to the spa. How do you deal with the water as it drains from the filter? As I'm freaking out, any advice is appreciated.