I have the bathtub faucet style with the pull knob on the water spout. That knob changes the flow from shower to bath. When I run a bath and have both the hot and cold water on, the showerhead pours water also. Just enough to splash all over everything. If just the hot, or just the cold water is on it doesn’t even drip. I have 3 tubs with this type hardware and all three of them do that. So I don’t feel that it is a problem with them being worn out. I think there may be an adjustment to make. Any help would be greatly appreciated as I could kill 3 plumbing problems with one stone. Thanks!!!
Have a licensed plumber install a pressure regulator on the inlet to your home. This will allow you to fine tune your pressure so that the water won’t spill out of the shower while you are taking a bath.
The alternatives to this may get messy because they involve chasing this problem into your existing plumbing if this is the only problem I would just reduce the pressure.
These diverters are designed to have the diverter button pulled open then the water turned on, if you dont as the button is pulled the pressure reaches mains pressure, they are not designed for that. It kills the rubbers inside. If thats the way the family uses them. Replace one, this will tell you if its the mains pressure or the rubbers inside are stuffed