In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
2 Pipe system - water hammer on one radiator
I've got an old home (1880) and we have a steam boiler in the basement (replaced in 99). Its a 2-pipe system with the old stand up cast iron radiators.
The 2nd floor bathroom has some terrible water hammer. It only happens during start up (about 5 minutes after the heat kicks on - when the steam first reaches that area). Its a loud banging sound - VERY loud. Its definitely on the supply line, before the radiator (somewhere in the pipe). Once the radiator heats up the banging goes away (About 2 minutes in duration) and wont bang again until it completely cools and another heat cycle is started. Meaning once its hot, I can continue to run heat cycles and it wont bang.
I've replaced the thermostatic trap and blew the return line out with nitrogen to clear any obstructions (that was before I realized it was on the supply side).
I dont know anything about steam and the couple of 'experts' I've had over have just thrown ideas at it without any success.
Any other ideas out there?
The piping for this radiator takes two turns. One from the boiler to the common wall in the basement. I've verified that I have good pitch on this pipe. It then heads straight up through a common wall to the 2nd floor, then takes another turn under the floor in the bathroom to the radiator. I suspect this is where the water hammer is happening. I've pitched the radiator on the supply side up as much as I can using spacers but the hammer persists.
Any other ideas? All of the piping in the basement has encapsulated asbestos around it. Happy to take pics if that helps.