Heating system and Hammer Drill noise

[howser]

Hi,

I hope someone can help, as the noise from my heating system is driving me crazy.

We recently had some building work done, during which our Worcester Bosch boiler was rotated 90 degrees, and new pipework was installed.

Multiple times a day, we hear a hammer drill-like sound lasting only about a second. It happens only after the central heating comes on—about 20 minutes or so later—but not consistently.

No taps running cause the noise; it only occurs when the central heating is active.

The sound is exactly like the first sound in this video:

.

Our heating system is a sealed pressurized system. The boiler and tank are about 4 meters apart on different floors.

When I’ve been near the tank as the noise occurs, it sounds like it's coming from the bottom, almost under the floor at the tank’s base.

The builders and plumbers have been great, replacing a few parts and verifying that valves are installed correctly, but nothing they've done has resolved the issue.

Any ideas on how to pinpoint the root cause? What steps could I take to isolate the problem?

Thanks
Howard

 

[blup]

Is there sufficient flow from tank to boiler?

 

[howser]

Flow from tank to boiler is fine.
Slowing swapping parts starting with the simplest things, no luck so far.

Just to add, heating/hot water working fine it just this hammer drill noise which occurs soon after the heating kicks in for the morning, happened this morning 3 times, about 10 mins apart and only lasting a second but is VERY noisey.