I,m new, so here are the basics. Underground vinyl pool, 1800 cubic feet, sand filter rather than diatomaceous earth. My brother has taken care of the pool for 20 years without a test kit and done great with only shock and chlorine. This year, he removed the cover and cheaped out by putting half the normal amount of shock in, and despite having our local pool pros analyze the water and give us a regimen of chemicals and exact usage instructions, and running the filter 24/7 for almost 2 weeks, the pool is still cloudy. We use a simple test kit and the PH is perfect, chlorine is slightly hot every day. We have seen a large improvement, but at this rate it will be July before it's clear.