Backflow preventer change out

[Jerry Ning]

Hello all,

I plan on changing my backflow preventer on my boiler. It is leaking in the vent port. Since I am replacing it wit the exact same watts 9d-m3, it is a simple twist off the 2 unions and twist back them on. My question is if I need to be worried about adding air into the system from the changeout. I can post a picture of my setup later today. Is this air amount something that the air scoop and air vent will take care of?

jerry

 

[Fitter30]

Valve the red handle ball valve off. It all depends how much water flows out of the expansion tank through the regulator valve but either way there isn't going to be a lot of air introduced.

 

[Sponsor]

 

[Jerry Ning]

Thanks for the reply. I will have the red shut off valve off. Also from reading the forum the pressure reducing valve has a check valve on it so the expansion tank theoretically shouldn’t drain at all. The only air I would be introducing would be the backflow preventer air. I’m basically paranoid of causing more problems with air in my system and having to drain/flush the system. I have a air vent on the boiler and an air scoop on the supply away from the boiler. The air added should bypass those vents till it goes completely back around 1 loop.