Vaillant ecoFIT pure 825 thumping noise

[Intoxicat]

Water in the gas pipe can make similar noises and if your gse says gas/air issue but unsure why, this would be worth checking.

Yet it happens nowhere near to the same extent with the heating as for the hot water, unless the hot water demands far more gas than the heating. Once the pipes are warmed up the heating is absolutely silent. It's obviously some kind of rare gas/air mix issue that's best left to the Vaillant specialist. I've looked at dozens of Vaillant boiler noise videos on YouTube and not one of them makes the the same noise as mine. There was one that was perhaps vaguely similar with an Eco Tec, but there was no follow up.

 

[dilalio]

unless the hot water demands far more gas than the heating.

It does.

 

[Intoxicat]

Here it is (drum roll) – what the world has been waiting for; the Vaillant engineer's report on the problem. The noise was due to an incorrect gas/air mix, but there were a few other issues as well, such as some grit in the pressure sensor.