Bought a house 2 years ago that sat empty for 2 years. This was the condition of the pool just after I purchased the house. Started the pump and filter in March. Had crystal clear water in 3 weeks. I was sure I would have to empty the pool and start all over. Thankfully, the plumbing was all in tact. Just had to install a new pump motor and cartridge filter and I was in business. Took a sample of my water to the local hardware store and followed every instruction they gave me to the "T". Lesson learned - when it comes to pool chemistry do exactly what the experts tell you to do. Don't think that you know better than they do. It worked for me.

Aside from stains due to all the algae sitting on the bottom (I scooped out 35 gal with a leaf skimmer) the pool is in fairly good shape.