No blowout port to winterize yard irrigation site.. Please Help!

[gordieax]

I traditionally blow out my irrigation system each fall to prevent freezing during winter. I've always blown out the system using the test cock on the right of the backflow preventer, however, after having had a new backflow preventer manifold installed last spring I've learned that blowing out using the test cock can cause damage to the valves. Looking at the exterior piping setup, there is no other port to attach my compressor hose to do the blowout. Should I have another hose bib cut into to the 1" copper pipe on the left of the back flow preventer to attach the compressor hose there? The existing hose bib at the bottom would only direct the compressed air back up through the backflow valve preventer. Any suggestions are greatly appreciated. Thanks.

 

[Twowaxhack]

 

[wpns]

Looks like you need to add another fitting.

 

[gordieax]

What fitting would you suggest and the best placement for it? Thanks.

 

[wpns]

I used an air-line fitting with a small ball valve. I’d probably try replacing that 90 with a tee but anywhere after the backflow is fine

 

[gordieax]

Thanks much