The house had one arrestor T’d off the water meter.
I added a second one before the ICG.
That pressure gauge was on the second hammer arrestor.
I tried opening the PRV yesterday. It just made the noise louder. That’s why it’s showing slightly more than 3 bar
Yeap going to get some plastic piping probs at weekend and see.
I did actually ring Caleffi UK yesterday - they were so helpful! The guy spent a good 30mins talking to me about the issue. He also thought the hammer was weird.