Depends on your back flow preventer. I’ve used ones that go to traditional fire hose threads and some in another city that goes down to 2in.
For fire hose thread buy an adapter from fire hose (I believe it’s 2.5 in) down to 2in.
From there do whatever you want with it…reduce down to 3/4 GHT or stay at 2in if your refilling tanks.
Or go straight to GHT.
Find out what threads your backflow preventer will have then you’ll know the best route…and if you plan on running a buffer off a hydrant or using it to refill tanks .
