Usually there's no such thing as "bad" sand, unless you've been through a Baq conversion or used some sort of additive that gummed it up--there are many folks on the forum that have used their sand for several years--I think Watermom is on her 7 or 8th season with hers, and the other two mods are over 10 years with theirs, if memory serves. However, if you're having sand blowing back into the pool and if that's been happening for some time, you might need to replace the sand that has blown out.

I'll let Pooldoc or one of the other equipment experts answer your filter question, but I'm thinking that 1.5 hp pump is too strong for your filter. I have a 1 hp pump on a 325# sand filter.....

One reason for sand blowback is too big a pump for the filter, but another might be broken laterals in the filter. Just something to think about...

Janet