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Water hammer and leakage/spray from multiple vents after new boiler install
We just had our boiler replaced (one pipe steam system) and kept all the existing radiators (7) and piping. On the first fire, there was severe water hammer that shook the floor and dirty water was shooting out of several radiator air vents. The system had started up fine a couple weeks prior with the old boiler (replaced due to leak requiring frequent refilling) and we have only ever had minor water hammer in the past. The hammer starts after the vents close and seems to be isolated to one run of pipe, which shakes visibly.
The water in the sight glass is tea colored. The installer added Squick before filling and firing.
The new boiler is rated to 65k BTU, the old one was ~110k. The installer had set the pressure to 3.5-5 psi; I lowered this to 0.5-1.5 which is what the previous boiler was set to. This didn't change anything.
I looked at the installation manual and the equalizer and Hartford Loop appear to be installed correctly.
Is this a problem with dirty pipes? Why did it just show up after changing the boiler? What else should I be considering?