I have recently installed a new variable speed pump and I saw that the old very large bladder tank have been replaced with a small tank. My plumber said that with VSD pump I only need a small bladder pump. When I ask him how do you size the bladder tank for the VSD pump and he just said that was all I needed.

Therefore, can anyone tell me

1. Why a VSD pump only need a small bladder tank?

2. how to size a bladder tank for the VSD pump?

3. Can we run the VSD pump without the bladder tank? I have tried with the bladder tank being isolated from the system and the VSD pump run as normal.

Thanks.