How much is the powerwashing vs. a new liner? After six years of algae, etc. in the pool, I wonder if they are not giving you an optimistic estimate of a 50% chance of a favorable outcome. I personally would use the money for a new liner, as I think it will be very difficult to drain the pool and remove the stains without causing significant damage. I have to admit, though, I have never heard of powerwashing a vinyl liner.

EricF