Air & noise buildup following a powerflush

[Aulus]

I had my old Vaillant combi & 8 rads professionally powerflushed 8 weeks ago, & Kamco Systemsafe DM was added. A fair bit of crud was removed, especially during the final SDS hammering stage! All rads left toasty & silent.

For the past few weeks I've noticed a fair bit of gas (not hydrogen) from the highest rad, needing bleeding every week, plus boiler is much noisier than it was at first. The engineer says the air is normal to start with, suggested I add a boiler silencer

I'm not for a moment suggesting he hasn't done the job properly, he was on site for a good 6 hours, but can anyone reassure me that the air & noise is common & system hush might indeed work?

Thanks in advance!

 

[gasbanni]

Should be quieter !

 

[ianniann]

They left you with a leak.

 

[Aulus]

Certainly should be quieter, I WANT it to be quieter!

A leak worries me, CH is pressurised at 1.5 bar. How would air get in?