I hate to debunk all the postings about the necessity to use chemicals but here is my experience. I installed a Sundance Montego spa in 1999. In the first two years, I followed the chemical regimen and testing. Then over a long period greater than six months, I became complacent about using the chemicals. I noticed that there appeared to be no change in the water quality. In fact, it was crystal clear and without any offensive odder. The slow speed circulation pump and ozonator are constantly on when the spa is not in use and the spa temp. was maintained between 102 and 104 degrees F. As a result of this experience, I decided not to use chemicals. In that period of time, I have only changed the water twice. Once in a spring where pollen from trees got in the tub and once in the fall because of leaves. The last time i changed the water was over five years ago. I do add water to compensate for evaporation. To this date, the water remains crystal clear with no odder and there has been no damage to any of the jets or pumps. I have had numerous friends, relatives and grand children using the tub and no one has ever gotten sick. Re all the postings recommending the use of chemicals, remember, suppliers want you to buy chemicals. One last thing, if you're in the start up mode (filing the tub for the first time) It might be wise to use chemicals to kill any bacteria that may be in the city's water system. I haven't found that necessary in my area. Regarding my ozonator, the original one installed in the tub uses a florescent bulb. I've had to replace that twice. I have now installed a Corona Discharge type that should have a longer life.