Anyone tried one of these filters?

I can't tell if it's legit or a gimmick.


http://www.spadepot.com/shop/Pre-Fre...FQioPAodUyoAmg

It does work if you have certain contaminants in your fill water but I think it would be more useful for drinking water than pool water. It is an activated charcoal/KDF filter. KDF is a copper/zinc medium that converts chlorine to chloride. It can also cause some heavy metals to "plate out" onto the medium. Activated charcoal is an adsorbent that can remove organics (which would be oxidized by the chlorine in the pool anyway.) If you have high iron content well water it might be moderately useful. There are several brands of these prefilters available but they all basically operate the same way. I have seen some in the past that contained "green sand' filter media which is specific for iron but don't know if these are still available.