GB315

You can't tell from the bubbles how much ozone is being produced. The ozonator produces ozone, but it is not under pressure. The ozone (along with air) is passively sucked into the circulation pump stream by a venturi tube. If you want to disconnect the ozonator, you need to unscrew the access panel of your tub. The ozonator is about the size of a large book and will have two nipples on it. One nipple will be connected to some tubing that snakes around toward the top of the tub and connects through some check valves to the circulation pump tube. Instead of messing with the tubing, all I did was unplug the ozonator from the electrical panel. I still get bubbles from the circ pump (because of the venturi tube), but there is no ozone it.

Interestingly, I have a Sundance spa (like the OP). I had a 100% CD with the ozonator plugged in, and 30-40% without it. Maybe the new Sundance ozonators are particularly powerful? It's simple to unplug the ozonator and see what happens with the CD.

I had this problem with a new tub too. It would eat all the chlorine in 24 hours with no usage (even after a decon). I unplugged the ozonator -- problem solved. If you search around this forum, you'll find some details about the interaction of ozone and chlorine. While the ozonator sounded like a great idea when I bought the tub, in practice, I found it too difficult to manage the chlorine. After turning it off, the chlorine demand has been completely predictable.

Thanks, QCD. I read that too and came to the conclusion that ozone should only be used with a continuous supply of chlorine.

New member here, but I wanted to add a data point to the ozone+chlorine question. Recently I bought a new 2010 spa with an ozonator. My intent was to use the dichlor/bleach method. For the first few weeks, with light use, everything seemed fine, although I did notice that the chlorine demand was somewhat high, >50%. After my kids had a hot tub party, I had a hard time getting the CC down, but since it had been about a month since the initial fill, I figured it was time to drain and refill anyway. I first did a 45 minute bleach decontamination to ~100ppm Cl, drained, then refilled, which left about 10 ppm. In 12 hours, there was no Cl. I figured that was because there was no CYA. I shocked up to 13 ppm with dichlor. That disappeared in 12 hours too. Suspecting the ozone was eating the Cl, I unplugged the ozonator and shocked to 13 ppm with dichlor. Voila! 12 hours later, the FC was 11 and continued to disappear at the rate of about 33%/day. With the ozonator off, I have not had any problem maintaining the chlorine level. So, my empiric test confirms QCD's explanation. I don't know if the Cl would be more compatible with ozone now that I have more CYA in the tub. I've now added a total of 3 oz of dichlor to the 500 gallon tub, so I should have 20-30 ppm CYA by now. When I bought the tub, I thought the ozonator was a great idea. Now, I'm not convinced. By adding another reaction to the chemistry, it would seem to make the Cl levels less predictable. Any thoughts?