We have a steam boiler that provides steam for most of the house but also has a hot water loop for the additions. We have been getting a lot of water hammer and it sounds as if it is coming from the area where the first hot water radiator starts (ie it is from the hot water loop). Does anyone have any ideas for how to fix this. We recently had our ancient boiler replaced but the problem is still there. Any advice would be greatly appreciated. Thanks!

((We recently had our ancient boiler replaced but the problem is still there))

If you had your steam boliler replaced I would call the company that did the work. Steam is NOTHING for a homeowner to work on. Call a professional before you hurt yourself or one of your family members.

NOTE steam does not water hammer but hot water does when it has air in the line. Shut off the unit and call for repair.

We are not planning on doing the work ourselves, I just want to have a better idea of what the problem/solution is before having someone do the work. Is air in the line a common thing? I was surprised that the water hammer did not go away when the unit was replaced.

Did you make the company that put your new boiler in aware of the air problem? If you did not you should have. See what they have to say when they fix it.