I have a follow-up question on that topic. I don't know when my filter sand was last cleaned/replaced, as I bought my house 3 years ago and it came with the pool. For the first time today, I opened the filter top and checked the sand. There was some residu in it, a bit like what you would find in cat litter - but smaller and, well, less disgusting! I was wondering what is recommended in terms of cleaning/replacing sand, when and how often should one do it. Note that last year, I did not have any cloudy water or sand in the water problem, and the filter seemed to work write. I just want to know if I should do something before the beginning of this season.
Cheers