I've just had a new shower installed, I've attached a pic of an identical one from the internet. When I turn the handle (marked red) for the handset diverter, the main shower head doesn't stop. Is this how it's supposed to be, that the handset is supplimental to the main shower but cannot be used alone? Also, if I turn the handset diverter handle all the way it shuts off all the water for both the main head & the handset. I thought the main on & off was on the valve itself and you'd just use the handset diverter to alternate between the handheld or the main shower.