So I bought my first house (1960's with a pool!) late last October - just in time to get the pool winterized and covered up. It was stained but I didn't really have any time to work with it. I took the water to a local pool store to see if it needed anything. Everything checked out OK and the chlorine was way high. The previous owners probably had it SLAMed to make it look good for the sale since it was too cold to swim anyway. So partially drained it, blew out the lines, etc and covered it for the winter.
Now that it's time to start thinking about opening it but I would like to get this stain taken care of first. The pool is concrete floor and steps with a vinyl liner on the sides. On;y the concrete portions are stained. The liner looks in good shape except it's bleached a bit. I've tried the Vitamin C trick as will as the chlorine tablet but neither does anything to the stain. I did, as an experiment, try pressure washing a small portion of the step (since the water level is low) and it did seem to help a little. It would certainly be a huge pain to do the whole pool.
Here are the best pictures I could get last night.
I was planning to drain and acid wash it but doing research this winter I'm scared to drain a pool for fear of it floating out of the ground and apparently draining a vinyl liner pool is also a very bad idea.
Any ideas what caused this stain and what to do about it?