Backflow assembly failure?

[Bob from accounting]

We have a Febco backflow assembly. (image attached)
When both master gate valves are tightened shut.
100psi water still shoots out of the center 3/4" T valves.
How is that even possible?
Thanks
Bob

 

[James Henry]

Your gate valve is not closing. Rust, trash,etc. Happens all the time.

 

[Sponsor]

 

[James Henry]

If you need to shut the water off, shut it off at the meter.

 

[James Henry]

Large gate valves usually require a pipe wrench to close them fully, if you don't know how then step away from the backflow.