Backflow output

Need some help here.....last fall a contractor winterized one of our systems by removing the backflow and blowing out the system, but last spring the backflow he reinstalled was not the one he took away. He took away a 1 1/2 inch and put back a 1 inch. He had to install reducing unions to make the connection. When I asked about it he told me it was a 1 1/4 inch backflow, not a 1 1/2 inch and that a 1 inch will put out the same volume and pressure as a 1 1/4 inch backflow. My question is, wouldn't a 1 1/4 inch backflow require 1 1/4 inch pipe and fittings? These lines are 1 1/2 inch. And, does a 1 inch backflow put out the same volume and pressure as a 1 1/4 inch backflow?
I believe we were flim flammed.
Nereus

The pressure will be the same regardless of the size. The volume will be less with the smaller backflow, but you'll still have plenty of water. My system has 1" from the meter with a 1" backflow into a 1-1/2" line to the valve manifold. Perhaps I don't understand your situtation. Do you own the backflow? If so, it seems to me the same BF should be reinstalled even though what was put in does work OK.

I would just call them back and have them put in the same size that was taken out.

Did he charge extra for the work involved in changing the pipe configuration? The lawn irrigation companies I install RPZ's for remove the RPZ and give it to the customer to store until spring time. There is no valid reason for what he did.