We have had nothing but problems with our Master spa since we bought it. Worst Spa ever!
We have to drain the spa at least twice a month or the water is green. Customer service is horrible as well. We have made numerous calls to the sales man who tried to diagnose the problem over the phone, we have replaced the filters and yet none has ever even came out to look at the spa.
One of the selling points on this spa was that you would not have to use chemicals but that couldn't be farther from the truth. Do yourself a favor and don't waste your money on a master spa.