Sorry to be late to the game but there are some misconceptions here that need to be cleared up. First of all our injector (yes, I work for the company) clicks once every couple of minutes at a volume that cannot be heard over the pool pump. If the pump is not running, neither is our unit.
Second, if you have 10,000 gallon pool and your pump is operating at 20 GPM. You will turn your entire pool over in 8 hours.
If you set our unit to inject at at 3 oz. per hour of 5.25% chlorine you will be injecting just 1 PPM. Depending on sunlight, bather load, etc. you may need to inject more.
Third, people using an electronic controller with a pH sensor can use our unit in place of an electric injector for muriatic acid and recieve enhanced reliability. We don't recommend using it for pH control without a controller.
I currently use one on my pool and I am injecting 5 oz/hour of 10% chlorine. I run my pool pump for 4 hrs/day (it saves me $24 per month on my electric bill). My pool is clean and the PPM is steady at around 2 PPM. However, it is only used infrequently by my wife and I and I have a birdcage.