Any 100% non chlorine hot tub options?

[chem geek]

One more option, if it's sold in the U.K., is Nature2 with non-chlorine shock (MPS). This link seems to indicate that it is indeed available in the UK (there are other sources as well -- you can do a Google search). The Nature2 uses silver (and zinc) ions which in conjunction with the non-chlorine shock provides enough disinfection to pass EPA tests, but only in hot water (i.e. for spas, not for pools). To keep the water clear you may still need to use chlorine once every week or two, but you can do that in between soaks and if necessary could dechlorinate before getting in again (and add MPS if needed).

[PoolDoc]

Does Nature2 no longer contain copper?

[chem geek]

Nature2 contains copper for their pool product, but it doesn't contain any copper in their spa product. That makes sense since pools tend to get algae while spas do not (due to lack of light with a tight cover and due to the very hot temperature).