... not so scarry after all! Here's some info for all of us non spa professionals.
I was able to get this info from their version of Vermonter and he is either a chemist or a chemical engineer by the way he knows chemistry.
Here is what I found:
Pseudonomas don't "just happen" in a tub. Even with an outbreak of bacteria (cloudy tub), there's no Pseudonomas growing unless it is introduced into the tub. The good news is Pseudonomas bacteria is easily killed as long as you keep the chlorine at acceptable levels (Vermonter always preaches this) but the bad news is that as CYA goes up the free chlorine (FC) becomes bound and becomes less useful. It can still kill regular bacteria but it can't kill the Pseudonomas unless you use high levels of chlorine. Once dead though Pseudonomas won't come back until reintroduced. Unfortunately, your tub can be infected by someone who goes into an infected tub, dries their suit (with humidity nothing dries 100%) and goes into your tub. Pseudonomas can be washed off bodies and clothing with warm, sudsy (soap) washing. I always thought that Pseudonomas would just grow in a tub.
Dichlor use is OK for killing regular bacteria and for killing Pseudonomas when the water is new but as you use dichlor (dichlor adds approx 1 PPM CYA for every PPM chlorine) the killing power decreases. I knew that for pools you need to increase the residue chlorine content as CYA increases. What happens in a spa is that within a month the CYA has risen to the point where very little FC is actually active. It's enough to kill bacteria as long as you give it sufficient contact time.
Now for something I will need to experiment with and think about - using bleach. Apparently, the reaction of chlorine reacting to the stuff it's reacting to is acidic and counter acts the higher PH of bleach. Although dichlor starts out as PH neutral the end result is it turns more acid which is why the PH and alkalinity drops in the tub. Now I didn't drink the koolaid (or bleach) as I originally thought it was crazy but maybe there's something there. Switching to bleach has only one benefit that I can see - it can kill the Pseudonomas bacteria even at 2 1/2 months out since there's no CYA in the water. It may even be cheaper but the only problem might be is the TDS which they claim only to be salt and salt may be a problem - though he claims it won't. Apparently salt is involved with the breakdown of any chlorine and using bleach would add 2x the amount of salt as using dichlor. So at 3 months out you would have 2 x the PPM salt than you do now.
As I said I have to think about bleach - all the other stuff sounds OK. The only real reason to switch to bleach would be for that Pseudonomas killing effect but I guess if I never experience it I really don't need to switch... more thinking to do on this. It wouldn't happen until AFTER the warranty expires! LOL
CYA in a pool can be a big problem but in a spa it serves no purpose and rises extremely fast. Use your tub 6 days a week, dose to 3 PPM and shock to 10 PPM on the 7th day and you would 6x3+10=28 PPM or close to the maximum you would want in a pool (or possibly spa)
I thought I would share my findings - I thought it was pretty interesting!
