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Help, mainly water hammer, but other questions

azogazog Member Posts: 2
Hi everyone,

Forgive what is probably a lengthy post, but I wanted to give as much detail as I can. I've done a bit of research, and even purchased the book "Lost Art of Steam" (which is kinda why I know about this forum), but am still working thru it.

The house is ~1915, a typical Four Square, nothing outstanding. As best as I can tell, the boiler for the single-pipe heating system was replaced in 2006 (or so the service stickers indicate). A year later, in 2007, my father passed away, and I "inherited" the house.

One of the things I do is routinely drain the boiler, mostly to get rid of the junk that builds up in the lines. Sometimes that takes care of the hammering, but it's been getting progressively worse. Some of the hammering is obvious, but there's also a lot of pinging, like a quarter is rolling around in the pipes, but I assume is the same phenomenon.

I've identified and fixed a few problems so far: replacing a non-working relief valve, and repacking the valve stem on another radiator (was hissing out of the valve).

I've attached two pictures of the boiler unit, one from front and another from the rear. I've put some text notes on them, let me know if I am correct or not:

The rear view, boiler-1.jpg:

there are two drain valves whose purpose I am unsure of. I've taken to draining those every now and again. They do get muddy.

I assume the short vertical pipe is the riser, going to the horizontal pipe which is the header. I guess the pipe going from the header back down towards the drain is the Hartford loop. There are two vertical pipes coming off the header, what I marked as "mains"; each going off to various locations on that side of the house.

The front view, boiler-2.jpg:

The drain below the sight glass is the main drain when I do yearly draining. You can't see, but the sight glass is at mid-point. There is another drain to the left of that which I also empty, when I can remember.

The pressuretrol was originally set at 0.5 and 2.0 PSI. I've lowered this to a notch or two under 2.0, not exactly 1.5.

In reading Dan's book, the magic number to keep in mind is 24" between the header and the middle of the sight glass. If I did my measuring correctly, it looks like this one is at 19". I don't know if that is the source of my banging. I read a little about the "false water line", but that's arcane to me, and not sure if that would address my issue.

Thanks for reading.


  • mcsteamymcsteamy Member Posts: 77

    Is the hammering and pinging in the pipes or in the radiators?  Is it possible to isolate it at all?  The piping might not be perfect, but it's a far cry better than a lot of systems that still manage to run without making a racket.  Have you checked the pitch on all of your pipes?
  • RodRod Posts: 2,067
    Water Hammer

    Hi-  Welcome to the Wall! I looked over your pictures and the labeling you have done appears to be correct. I've posted you pictures below with some added labels.

    The Boiler Piping looks reasonable. There seems to be some sort of fitting (other than the pipe union) on the equalizer pipe though I can't see what it is?

    Do you have main vents? If so what type are they and have they been serviced lately?

    Banging - Where does it occur? in the radiators? In the boiler? When does it occur? At the beginning of the heat cycle (when the burner comes on)? Midle of the heat cycle? End of the heat cycle (When the burner shuts off) ?

    Could you post a picture of the boiler piping where the risers from the Header connect to the mains. Take the picture from farther back so we can trace out the piping.

    Skimming- Has there been work done on the boiler recently? How is the water line in th glass sight tube behaving? Is it bouncing a lot when the burner is on?

    What other questions do you have? 

    - Rod
  • Jamie HallJamie Hall Member Posts: 6,653
    As McSteamy said

    I've seen a lot worse.  That's not a bad looking setup, basically.  As you note, the distance up to the header may be a little short, but that's not a real killer -- and with the vertical takeoffs to the mains shouldn't be a major issue.

    And you've set your pressure about as well as you can with a pressuretrol.


    Again, as McSteamy said, the very next thing to do is to check the pitch of all your pipes.  Carefully.  Section by section.  Since you have the Lost Art, you will find in there tables which give you the correct minimum pitch for the various pipes.  Spend a little time while you are doing this making sure you know which way the steam is going in each pipe and, perhaps more important, which way the condensate is going.  Be sure to look for sags and low points -- even if the end to end pitch is right, a sag can cause real problems.

    Correct any pitch problems you find (take a look at a thread of mine -- "water hammer -- and object lesson" for just how critical pitch can be; that thread describes a situation with really wild water hammer which was corrected by changing the pitch by just a half inch in 20 feet).

    You don't really need to routinely drain the boiler, although you do need to make sure that the low water cutout is clear -- if it's a float type, it will have a drain on it; just dump a couple of quarts out of there every couple of weeks.  A full drain and refill on the boiler just isn't necessary at all, unless your pipes are unbelievably bad -- which they rarely are.

    Technically the vertical pipe from the header down to the drain is called an equalizer.  It does two things: takes any water brought up in the riser back down to the boiler where it belongs and, more important, equalizes the pressure in the returns.  The short nipple about at the level of the water line is the Hartford Loop connection; and at the end away from the boiler it drops down to a wet return.

    A false water line is an arrangement of pipes used to raise the apparent water line in return piping when the boiler water line is too low.  I doubt very much that you need one here; that problem doesn't usually show up as hammering but as really bad heating.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • azogazog Member Posts: 2
    additional info

    Thanks all for the replies.

    There's actually several different types of noises. The pinging appears to be isolated to a specific section of pipe going to one specific radiator. I did try to close the valve on this radiator to see if it addressed the pinging, but I don't think it changed anything.

    I will pay attention more closely to when hammering occurs. Some of the other noises appear both at start up, and shut down. During heating, it appears quiet, other than the pinging above. At start up, I hear knocks (not really a metal-hammer sound). After the cycle is when I hear the bigger bangs that wake me up.

    I've added two pictures here: One is as far away from the boiler as I can get, hopefully aimed to see the two pipes coming towards me. I am taking it that the upper pipe is the supply and the lower pipe is the return. This lower pipe is sloped and hung by a chain.

    There is also what I figure to be a pressure release valve on this lower pipe. There are three of these in total (that I can see). I took a close up of this in the second picture. It does not seem like there is any maintenance function on this? There is a nipple or something on top, but it's sealed.

    I do not know if there has been any skimming. At least, I know I have not done so. Since the unit was installed for less than a year before my father died I am going to say that he did not skim it either. The water in the sight glass doesn't bounce, it seems to be pretty stable.

    As for the fitting on the equalizer pipe, I do not know what that is. It appears to be a nipple or something.

    I'll continue reading the book, and tomorrow I'll see if I can start checking the pitch. Thanks again!
  • RodRod Posts: 2,067
    Main Vents

    Hi- What you are calling a "pressure release valve" is what is know as a main vent. The purpose of the main vent is to allow air to escape from boiler piping but not steam. When the burner turns on and steam starts being produced the steam forces the air in the pipes out the main vent but when the steam reaches the vent, the main vent closes and keeps the steam from escaping.  Each steam main needs to have a main vent. If it is a long steam main it may have multiple steam vents.  The main vents are usually located at the farthest end of the main from the boiler and a lot of main vents are located on the return piping just before it drops down to floor level.  Your vents appear to be located on the return piping. Do all you mains have a main vent(s)?


    Here is a good link to how main vents work:

    This website is Gerry Gill's, a very experienced Cleveland steam pro. Look around the site as there is  a lot of good information on residential steam systems.

    I noticed that your steam piping doesn't have insulation. Insulation really saves on fuel so yo may want to consider insulating  the steam piping sometime in the future.

    Here is an article by Dan on the benefits of insulation:

    There is a lot more good information on insulation in past posts on the Wall.

    Do you know about sloping your radiators?

    - Rod
  • Jamie HallJamie Hall Member Posts: 6,653
    It is quite possible

    that what you are hearing -- or at least some of what you are hearing -- is expansion and contraction noise, rather than water hammer (which tends to be either startup or cooldown, but not both, except once in a while it's the whole cycle).  These noises can be remarkably loud.

    Look for places where the steam pipe can rub or bind on something in the house...

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
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