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Union in the Return

Polycarp Member Posts: 135
As I mentioned in a previous post (<a href="http://www.heatinghelp.com/forum-thread/131134/Phase-1-2-complete">http://www.heatinghelp.com/forum-thread/131134/Phase-1-2-complete</a>), I need to replace the drip line on the main of my one-pipe steam system.  I'm going to have to cut the pipe out, so I'll need a union to get the new pipe in. 

This has left me thinking, does it make any difference whether the union is above or below the water line?

Along the same lines, Steamhead recommended that I up the drip line size to 1".  Each riser (3 total) has its own drip and the 3/4 is original to the system, so with these in mind, would this still be necessary?

Thanks in advance.


  • Unknown
    edited June 2010
    Follow Steamhead's Advice!

    Hi -

    A tight union is a tight union, however, given the choice, I’d put it above the water line. That way it’s not in standing water and if a leak developed, it would have less consequence.

    Regarding the drip size- Steamhead ,who is a very experienced steam pro, replied to you that “The drip from the main is too small, make it at least 1-inch.”.  From this I would take it that you need at a  minimum a 1 inch pipe and it might be a good idea to even go up a size. I'd definitely follow his suggestion.  Size wise- a 1 inch pipe is 2.05 times larger than a 3/4,  a 1/14 inch pipe is 4.3 times larger than a 3/4 inch pipe.

     Keep in mind that the guy who originally put it installed the piping was the lowest bidder and his thought was probably keeping everything to the minimum that he thought he could get away with rather than the optimum so I wouldn’t necessarily follow what he had done.

    - Rod
  • Steamhead
    Steamhead Member Posts: 16,842
    edited June 2010
    Thanks, Rod

    3/4" is really too small for a drip unless you.re just dripping one radiator and a little bit of pipe. You have more than that so 1" is minimum. All you need to do to accommodate the change is to replace the 1-1/2"x3/4" reducing ell at the end of the branch with a 1-1/2"x1" one.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Polycarp
    Polycarp Member Posts: 135

    Thanks Steamhead. I was inclined to follow your advice even though I wasn't sure, but now I am.

    Ultimately I'll probably have to replace most of the wet return. Until then, I'll have to put in a reducing coupling to adapt the 1" to the 3/4" connection on the horizontal in the wet return.
  • Polycarp
    Polycarp Member Posts: 135
    lowest bid

    Above the water line was my inclination as well.

    I'll be following Steamhead's advice about the size. I just wanted to understand why, not just what.

    The original system is not original to the house, but was installed soon after (the original gravity air was not ready for prime time). While the subsequent alterations were pretty hackneyed, the original installation seems pretty solid .. there's even a custom-built radiator made to fit the angles in a bay window. I wonder if it was a low bid situation or if the smaller drip was all that the original coal boiler with its long, slow burn needed.
  • Unknown
    Steam Info

    Here are a couple of interesting books if you are want to learn more about  steam.

    "500 plain answers to direct Questions on Steam, Hot Water, Vapor and Vacuum" by Alfred Grant King 1915      263 pages   Note: -Great drawings! Helps you understand the "Deadmen's" thinking.  Down load as a PDF as it is easier reading this way.


    Burnham Heating Helper - Has pipe sizing.

    - http://www.usboiler.burnham.com/PDF/htghelper.pdf
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