Changing the water only once per year is absolutely not enough. Twice per year would be a minimum for hot tubs with average usage. Again, changing the water is great for ridding the tub of high TDS levels. Water maintenance and clarity is greatly enhanced when water changes and plumbing purges are performed at regular intervals. Hot tub owners need to use an effective "purge" or "flush" product just prior to draining. Just draining and adding new water is foolish without cleaning the plumbing. No matter what you use for water maintenance or whatever sanitizer you choose to use on an ongoing basis, there will be "Biofilm" lurking within the system. This is known science. Many dealers try to downplay the need for using plumbing cleaners and I cannot understand why when there is a plethora of scientific data that shows the need to use a good and effective cleaner. Biofilm is like plaque on your teeth. You brush daily and eliminate most of it. You need to "chemical" brush your plumbing and jets to eliminate or reduce the bio-buildup. Please read about biofilm in hot tubs. Hot tub owners who follow a "purge & drain" protocol every 4-6 months have much easier maintenance and much higher water quality feel and clarity.
