I have spent the past 10 years restoring a historic Victorian house, divided into apartments since the 1930s. I live in the top unit, and rent the 1st and 2nd floor flats to tenants. In 2013, I replaced the failing old boiler (Slant Fin) for my one/two-pipe hybrid steam radiator system with a new Crown boiler. Immediately after, my tenants and I experienced the violent noise of “water hammer” in the pipes in the basement. The old boiler frequently broke down, but the pipes had been quiet. My trusted heating contractor insists that the water hammer is normal. I know it is not, and have read a great deal about it. I wrote him a positive letter pleading for help, but he responded by saying it gave him a good laugh. Unfortunately, there are no “Dead Men” – aka steam experts– left in my city or within a 100-mile radius to help me. I am on my 3rd set of tenants since the water hammer began, and they have asked me to fix it. I wish I could but cannot find anyone who can. I wonder if the pipe heights, like the Hartford Loop, were set for the old boiler, and thus are off-kilter for the new boiler?! I have made sure all the 1-pipe radiators are pitched toward the supply and the 2 pipe radiators are pitched toward the return and have replaced all the radiator air valves. The erratic water hammer comes from the cast iron horizontal pipes and/or the steel and copper return lines near the boiler in the basement – not from any of the radiators. There is no rhyme or reason as to when the noise occurs like the beginning or end of a cycle. I can not make the system behave badly when contractors come over to see if they can fix it. I have tried to upload some photos, but this site says the jpg images are not valid for some reason.