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 Steam radiator vent spitting water
Author: Anonymous User

A customer who just had a new steam boiler put in called us because a radiator air vent literally flew off the radiator (the vent broke off at the threads). I checked the pressuretrol setting on the boiler, the cut-in was set a 9.0 psi, with a 1.5 additive differential. I reduced the cut-in setting to 0.5 psi and replaced the radiator vent. When the system got up to pressure, the vent began spitting water. There was severe water hammer in the radiator (steel-fin on steel pipe convector) and also in the uninsulated steam main. The radiator was pitched properly (single-pipe system). Every time the water hammer kicked on, water spit out the vent. But I'm not sure what's causing the water hammer. I also noticed that the boiler shut down on low water, but the water level came up again as the boiler cooled. There was also a lot of rusty gunk on top of the water in the sight glass (the boiler was only replaced about four days earlier). What's wrong with this system?

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 Re: Steam radiator vent spitting water
Author: Shoemaker2 (MA)


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 Re: Steam radiator vent spitting water
Author: e-plumber (NY)

It sounds like wet steam is being carried up the mains to the rads. causing the hammer and spitting from the air vents. Is there a skim valve on the boiler, there could be a film of dirt or oil on the surface of the water (dirty sight glass) which could complicate things as well. All rad valves on a one pipe system should be in the fully opened position to help the condensate drain back properly.


P.S. How did you make out with that rad valve on the hot water system?


"The society which scorns excellence in Plumbing as a humble activity and tolerates shoddiness in philosophy because it is an
exalted activity will have neither good Plumbing nor good philosophy: neither its pipes nor its theories will hold water." -
John William Gardner 10/8/1912 - 2/16/2002

Repair your leaking Plumbing fixtures ASAP [www.theplumber.com]
This slow drip will waste 7+ gallons of water per day.

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 Re: Steam radiator vent spitting water
Author: Anonymous User

E-plumber, check out my follow up posting tomorrow (Thursday).

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 Re: Steam radiator vent spitting water
Author: mikeinpa (VA)

I would agree with e plumber ,sounds like wet steam ,was the boiler skimmed if not ,skim the boiler also check the near boiler piping to boiler specs,are there any main vents ,try .5 cut in with a 1psi diff.

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Service plumber northern va

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