roof thank line banging like crazy

tino1980

hello everyone.
I have a building in Manhattan that has a steam line going to the roof tank so the water wont freeze, now the line is making a banging noise louder than a 45 caliber shot gun, I lower the pressure in the boiler that was at 5 PSI, that solve the problem for 4 weeks until this weekend that is very cold the problem returned and now worst than ever.
Its a 1 pipe system and its heating 2 roof tanks from 1 steam riser.

It seems to be that the building had the same problem before since last winter they had that very same riser exploding in the middle of the day creating a sauna in that apartment.
I checked pitch, air vents and everything seems to be ok.

what could be creating this extreme noise????

nicholas bonham-carter

Without a piping diagram, we could be shooting in the dark here, so maybe you need a good steam pro to look at this, Gateway plumbing) is one quality pro in NYC.
It would be a good idea to take whatever steps are needed to fix this, not only for the comfort of the tenants, but als to reduce the impact water hammer could have on your piping and the tanks themselves- how many gallons are in there which could rain down when they rupture?
Is there a vent at the top of the riser feeding the tanks?
Is there a horizontal pipe on the way which has sagged causing a water seal n the way up? You say the pipe pitches are ok, but have you used a level? Where is the banging occurring-in the tank?
Your building, if the main venting is adequate, should be able to heat evenly with a few ounces of pressure, so crank the pressure trol down as low as it will go, with the pressure verified by a good low pressure (0-3 psi) gauge. You may be burning twice the amount of fuel necessary without good venting.--NBC