Why are diverters built this way?

[kb22]

Hey folks,

I have a diverter valve for my above ground pool right before the water drains into the pump. For my setup, 3 attaches to pump, 1 comes from skimmer and 2 comes from main drain.

I want to block the main drain for vaccuming but those two nubs with screws in them block me from moving the dial from 4 to 2.

What is the proper way to move the position and why are they designed like this?

 

[ajw22]

You can unscrew the top and rotate it so 2 is over your pump pipe, where 3 is now.

Then you should be able to rotate the valve over what will be 4 and 1.

The purpose of the stops is to keep you from accidentally blocking all flow from your pup, which could damage the pump or plumbing.