The pressure will increase as the filter clogs, it is harder to push the water through the filter. Would it be easier to drain the pool and start fresh? That is what I would do, but I don't have an inground pool, the water pressure on the outside of it could cave it in or float it, and I think it will depend on your location, how dry it is in your area, etc. I managed to close my pool correctly last year, and it opened flawlessly this year, but in previous years when I did not close it correctly, rather than spend hundreds of dollars on chemicals, I drained it. But I have an 18 foot above ground, so it is not to much of a big deal.