Reduced shower preasure on diverter change?

I live in a apartment and I have a shower that has three parts. The top part is the shower head, middle part is one of those 'twist' water control things, and the bottom part is the diverter/spout.

The diverter/spout was leaking a bit when the shower was on so my landlord called a plumber. The plumber spent 4-6 minutes in my bathroom and changed a leaking diverter with a new one. Since then the water preasure has been weaker out of the shower head (I expected it to get stronger as no water is going down the faucet).

What is going on? How is it physically possible to have weaker pressure with only a diverter change? Id say its about 20% weaker.

Its the same faucet (and he only spent about 5m in there anyway) and same shower head. Theories?

edit: And there is also about 2x more water out of the faucet then the top of the shower without a showerhead.

I'm gunna guess that when the plumber replaced the diverter, he dislodged a bunch of calcium particles, and now they are clogging up your shower head. Try removing the shower head and cleaning out the backside....you might also try spraying some CLR to help dissolve these chunks of crud.

I half considered that. I basically took off the showerhead and tested the waterflow. It is about 2x what comes out compared to having the showerhead on (im guessing 2 gpm vs 4 gpm, while the faucet is probably about 6 gpm).

I even purchased another showhead (another 2.5 gpm) and it is also weak'ish..

But maybe some of it (calcium ) got stuck in my original shower head, and this new one is a fake 2.5gpm???

What is your water pressure. You can buy a gauge or about $10

Not sure what my water pressure is, but I just went in and drilled holes in two of my three showerheads, and WOW, they both work so much better. I am getting GREAT pressure and lots of water.

I did the same. The new shower heads are designed to save water but to me, it's akin to peeing into a fan. I drilled out that puppy, and I also have great water pressure. I just hope the water cops don't arrest me for doing so!