This is what my CH sounds like...
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is quite loud. It is not a gurgling air sound. But more a rushing around like billio sound! I've got a setting to reduce flow, but it is supposed to be self regulating anyhow. Boiler is brand new combi and whole system has been flushed and I'm confident that it was done well. Is a noise reducing additive going to be useful? What else do you need to know?15mm copper with 22mm from/to boiler and between floors.