I will be using the filter on a waterfall fountain with a small basin. The filter will be connected on a valved bypass line off the waterfall source line. The filter will function when the fountain pump is running. The fountain pump runs approx 4 - 5 hours a day, over 12 hour period. Is there any problem with the UV lamp being on when the pump isn't running? I would probably use the 12 hour setting for the UV Lamp. Does the UV lamp turn on and the 12 hours begin when you plug in the lamp?