Cl concentrations in pool vs. spa

All,

After reading horror stories about public hottubs, and the fact that the typical 4-5ppm Cl in a pool equates to a very very tiny amount of total Cl when that concentration is in a spa, I want to keep my Cl concentration much higher in the spa vs. the pool (say 10-15ppm vs. 5ppm in the pool). But I only have one pump, one filter, etc. and my returns go to the pool and the spa, so that the spa and pool are effectively one big body of water into which Cl is added. How can I keep the Cl levels higher in the spa all the time? Should I just *never* allow spa spillover, thereby never mixing spa water with pool water, and monitor Cl levels separately? That sounds pretty labor intensive and I imagine I'd be constantly adjusting water level and Cl level in the spa. How do others do it?

I'm pretty sure those hi Chlorine levels are for isolated spas that stay hot all the time, and have a high bather load.

I keep my spa the same as the pool.. there is a pool return for a "fountain" that feeds the spa (overflow) so it always has a fresh supply of CL. I usually don't check the SPA.

Actually, currently my SPA fountain is plumbed to my solar heater, so the SPA doesn't get constant CL. I've programmed my computer to start the filter pump and run in "spillway" mode (suck from pool, dump to spa) for 30 minutes. It takes me 15 minutes to fill my spa, so that 30 minutes is pretty much a total water change daily.

Robert