Trickling water sound in new boiler

13 Apr 2012
Reaction score
United Kingdom
I've recently had a new combi boiler fitted (it replaced an open vented system) and when it starts up on a demand for CH, there's a reasonably loud splashing/trickling water sound from inside the boiler. It sometimes extends to the flow pipework. The noise in the boiler dies down after a few minutes but if you listen closely you can still hear trickling water noises every now and then. The boiler is holding pressure OK, no leaks underneath it and radiators are heating as expected, inhibitor was added. The system has been fitted a few weeks now and I had expected this noise to gradually disappear as I thought it was air.

I had mentioned it to the RGI originally upon commission as it did it when it first fired up but he wasn't concerned and just said air will make its way out of the auto air valve. Obvioulsy I can't check this as it's internal to the boiler and I'm not allowed to remove the front cover. Likewise I can't bleed the pump either. I've bled the radiators on a few occasions now and got a little air out, but the boiler 'splashing' noise continues.

Anyone got any ideas? How long does it take for all the air to be expelled from a CH system after a full drain and refill? Could it be anything other than air?
Sponsored Links