Theoretical If Chlorine Drops To Zero Using Ace

[AnneM]

I invested in the ACE system for my Jetsetter mainly because we'll be away for seven weeks over the summer and various family will be staying at my house. It seems the easiest way of ensuring the tub is manageable for guests who won't be familiar with maintaining it. Basic instructions will be left and I intend to refill when we get back. How big a problem would it be if the chlorine level dropped to zero and then went up again between guests? The tub also has an ozonator (I like the bubbles!) and EcoOne (for my skin).

[chem geek]

The risk is low, but not zero, that you'll have problems if the chlorine level dropped to zero for an extended period of time (many hours, not just a few). The reason is that water passing through the ACE or ozone systems would get disinfected, but the bulk spa water would not so bacteria could still grow on spa surfaces. However, the ACE system uses salt in the water to produce chlorine, not just hydroxyl radicals, so if you set it for maintaining chlorine during non-use, then the issue is how long the chlorine level would get to zero from bather load. Note that the ozonator actually uses up more chlorine when there is no bather load.

If I assume you had the ACE set to maintain around 2 ppm FC with no bather load, then if you only had one bather for 30 minutes, then that might be OK, but if the bather load was higher than that, then it could use up the chlorine in the spa perhaps for a day and if they were to soak consecutively on multiple days then the chlorine level would likely get used up completely. The ACE and ozonator would kill whatever is in the water that circulates through those systems, but they won't do anything about bacteria growing on spa surfaces unless you have a chlorine residual.

Worst case, biofilms could form on spa surfaces and in piping before the ACE and ozonator systems (but probably not in piping right after those systems). The water itself would likely remain clear from the circulation through ACE/ozonator systems, but the spa surfaces might feel slimy. When you get back, you could use Spa System Flush and/or super-chlorination to get rid of such biofilms and then drain/refill the water.

The odds are probably low that things will go south unless the bather load is high. Is there any reason why your instructions don't tell them to turn up the ACE system (does it have a "boost" mode or something like that?) right after they soak?

[AnneM]

Thank you very much for the quick reply. I realise the ozonator isuue but don't want to complicate things by disconnecting it. Bather load is likely to be one, or at most two, reading a book for a while. My instructions will include "boost", but as I don't want to stress my well-meaning but over-anxious sister-in-law they will be very simple! I'll certainly super-chlorinate before refill when we get back. Hopefully things will work smoothly.

Canada, here we come!