Quote Originally Posted by CarlD View Post
So, if they recommend a 150# sand filter, on an IG pool, get a 200#. On an AG pool get a 250# filter.
Actually, Carl, that wasn't quite how I meant it.

What actually happens is that the 'recommended' filter size for, say a 20,000 gallon IG pool, is a 22" filter (at 15+ gpm/sft). But, due to some games the industry played with the NSF, the 'recommended' size for a 20K gal AG pool (at the 'rigged' standard of 25 gpm/sft) is about an 18" filter.

But, what you NEED for either pool is a 24" filter, which gives you about 13 gpm/sft.