Hi hope there can be some ideas here. I went to a job oil (heatslave 20/25 combi ) the pipework was chattering or banging very quickly intermittently but especially when cold tap was run at the same time. The flow switch was leaking badly so I changed it and the noise from the pipework stopped. 4 hrs later had a call and the noise was back. Long story short if you push the taps head on the hot pillar tap inwards the noise stops. I have ordered a set of ceramic valves as I'm thinking it must be chattering away on the seat when in use due to wear, and this is transferring through the pipework, my question is why this would happen and would a shock arrestor or something else help as the tap is only 2 years old.