Not quite sure what a small spa is. I use this in my greenhouse to reduce Ca. It does help. Remember it just reduces, doesn’t completely take it out.
I think it can be used on any water line fed by a garden hose connection. I use mine on the input of my patio misting system.
Yes. The threads on this filter are 3/4" GHT (garden hose thread). The female end has a gasket in it just like a hose nozzle or sprinkler you would thread onto your male hose end. The outlet is male threads of the same type, that you could attach another hose to.
NO I just replaced my A/C because I did this for 2 summers. It does help cooling until it runes you condenser. Believe Me don't do it!
Hawk, that is difficult to answer in this forum because the quality of water can vary from area to area. We do recommend that you replace your filter at the beginning of each season, though, as a sort of catch-all.
Ken, we do not recommend this. If the CLR were to somehow get into the mist line, then CLR would be mixed in with the water that is sprayed onto everyone.
Joe, we recommend you replace your filter annually. If you live in a very high hard-water area, you may want to replace it twice a season to prolong the life of your misting system.