I have a Moen in my shower and a spout with a diverter. When I run the water with the diverter open, there is still a lot of water coming from the shower head. The only thing I can think of is that the water pressure is so strong that the water just gradually builds up and comes out of the head.? Or should I just go and buy a new cartridge and see what happens? Ive been in maintenance for years now and this one has me stumped...

Any suggestions would be great Thanks