I had a saltwater pool built this June and had several issues with the contractor that were eventually settled but not before I threatened legal action, however I am now having trouble getting answers back from the contractor now that his original obligation has been completed. (Big Surprise) I was told by another pool owner that the filter must be purged every couple of months, or when the pressure gage exceeds 10psi. And if not done it will ruin the filter. Is this correct, and if so how is it done.