Backflow Preventor for fresh water supply

[MikeT]

Hi All,

Has anyone replaced the backflow preventor where the fresh water supply hose attaches?  I can't get it apart to install a new one.  I have attached pictures of the front and back of the housing.  Here's the sad part, I did replace this item in 2016 when I pushed the valve (white part in the middle) while the system was under pressure.  I just cant figure it out this time. 

Alternatively, could I purchase an in-line one that might be easier to install?

Cheers

Mike

[Merlin]

Is that blue part inside a large plastic c-clip?  Does removing it help?

[MikeT]

No, there are two pieces of plastic that ar meant to keep that brass part from spinning.  I did fix this by punching out the broken backflow preventer and adding a new one (much better) and a barbed fitting.  It's quite long but it all fits nicely inside the pump closet.  Thanks for responding Merlin.  Here's picture of the final result.