I just got a Tiger River Sumatran spa, and had the Freshwater III ozone system installed with it. When it was first plugged in it was quiet (yesterday). Today, I can hear the water circulating under the shell, and can even feel the vibrations from it circulating. The air was flushed from all the lines at installation (professionally installed). I was told by the dealer that this sound (like when yuou get into a regular bathtub and the level gets to high and it's draining through the overflow) is normal for the ozone system because the circulator pump is moving water all the time and that if I turned off the ozone system it would stop.

Is it really normal?

In addition, there is a hissing sound from the control panel area, and I was told this was the ozone system generator.

is this really normal?

I'd appreciate your help. I'm confused because this wasn't happening day 1.

cheers

Circulation ozone systems often 'gurgle' as the ozone starts to form larger bubbles prior to spa re-entry
no explanation why it could change - you probably just didn't notice it

the buzzing sound is normal if your ozone is corona discharge spark generator style - 120 sparks per second (60Hz = 120 high/low spikes)