Tarm Thumping

On my Atmos the back of the boiler needs to be raised 10mm higher than the front to facilitate air bleeding. Don't know if this would help with yours. Randy

I had that problem with my tarm, adjusting the leveling legs so the boiler is pitched toward the vent helped, but what finally did the trick was to install an auto-vent in the vent tapping. No problems since.

Look at some of my old posts. I had similar problem.

I had a similar thing and it was the fiberglass rope that seals the refractory base to the metal was missing in a spot. Replaced a section of rope and no more thumping.

Put on a ball valve before the auto-vent. That way if the auto vent starts to leak, its easy to replace.
This fix should work, it did for me.

Between the metal and refractory base that hold the nozzle, there is fiberglass rope. It should be down a ways, but some how one end made it to the surface of mine and pull up. I noticed it this spring when I was cleaning my boiler up for it's summer vacation. At then end of last winter I had some thumping, but after fixing the rope gasket, I haven't had any thumping this fall.