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Steam piping

Luis Member Posts: 20
Hello everyone,

I've been reading "The Lost Art of Steam Heating" and verifying/correcting my home steam system. Unsurprisingly, many of the details were overlooked by previous installers such as main take-offs at 90 degree, too high of system pressure: 4 psig (2 psig cut-in + 2 psig diff), plugged main vents, insufficient header length devoid of swing joints, etc.

So far, I have changed all the take-offs to 45 degree as recommended, verified all the pitches, confirmed that connected load with proper pick-up factor can be sustained by the boiler, and I am in the process of correcting the near boiler piping and end of main vents. Could someone please advise on the following?

1)The ends of the 2” “U” shaped main located in the basement used to connect to the existing 1-1/4” wet return via two 1-1/4”x2”x1-1/4” tees. One of the 1-1/4” ends at the tees was provided with 1-1/4”x3/4” reducing nipple to allow installation of main vents. The installation was similar to the depicted on page 115. I have located the end of main vents 15” from the end on a 2”x1-1/4”x2” tees using 1-1/4” six inch long vertical nipples to 1-1/4”x3/4” reducing concentric couplers to ¾” NPT vents in efforts to avoid superfluous bushings and leaks. I am aware of the fact that the velocity of the steam will increase when transitioning from the larger to the smaller pipe thus would it be advisable to install a 1-1/4”x3/4” bushing on the tee and have the complete main vent assembly on a ¾” pipe?

2)In connecting the modified 2” main to the existing 1-1/4” drip connections, I was considering using two new 2”x1-1/4” reducing 90s. Or, installing two 2”x2” 90s, 2” drip connections, and reducing from 2” drip connection to 1-1/4” wet return below the boiler water line using a 2”x1-1/4” reducing concentric nipples. Honestly, I am more inclined for the latter option, but what is the impact on the system operation if a) a 2” drip connection exists until below the boiler water line, b) if drip connection reduction occurs at boiler water line, slightly above it, or at end of the main?

3)If I am to make the transition from 2” to 1-1/4” for the wet return below the boiler water line, I concerned that the necessary 2” union will lead to future leaks. Upon various measurements from the leveled ceiling, I have ample clearance to lower the wet return a couple of inches so that the boiler water line shifts from the wet return to the base of the drip connections. In doing so, the 2” unions could be installed in the drip connections avoiding leaks and yet reducing the size of the wet return below the boiler water line via a 2”x1-1/4” reducing concentric nipples. Moreover, I am conscious that a minimum of ½” per 10’ pitch is required for the wet return and that the pressure control has to be adjusted to 2 psig yielding a 28” “A” dimension minimum.

4)The manufacturer recommends 24” from the center of the sight glass to the header, two 2” risers, a 2” header, and a 2” equalizer. The previous installer overlooked the 24” and installed the header 14” from the center of the sight glass, with a couple of bullhead tees, and no header offset. I am redoing the near boiler piping following the manufacturer’s recommendations except that I would like to increase the distance from the center of the sight glass to the header, as there is available space. I would like to increase the size of the header one size from the recommended 2” in which case would it be 2-1/2” or 3”?


  • Steamhead
    Steamhead Member Posts: 16,714
    Luis, you really are picking this steam stuff up!

    To answer your questions:

    1. I have seen main vents installed both ways you describe, and either way seems to work fine. Your present arrangement should not cause any problems.

    2. Many old piping diagrams carried the drip the same size as the steam main until it got below the waterline, but again I have not seen any performance disadvantage of using a smaller drip. Either way should be fine.

    3. If your present "wet" returns are actually ABOVE the boiler waterline, they need to be lowered. It is essential that all drips extend below the waterline before joining together, since steam can enter the returns and cause banging if they don't.

    4. The 24" rise above the highest possible waterline and the 2-inch header and equalizer sizes are minimum figures. Increasing these dimensions will not hurt anything, and will actually make the system work better by better drying of the steam. Consider using a "drop header" which is much easier to put together, and will allow even higher risers. Go to:


    to see some fine examples of drop headers.

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  • Luis
    Luis Member Posts: 20
    Please read


    Thank you for the reply.

    In reference to the wet return being above the boiler water line, my current layout is such that my main is ran in the basement in a "U" shape. The boiler is located halfway at the bottom of the "U" an the drip connections at each end of the "U". The bottom of the drip connection on the right had end of the "U" coincides with the boiler water line whereas the drip connection of the left end of the "U", 20' apart, is below the boiler water line. Is such arrangement acceptable or should both drip connections be partially below the boiler water line to ensure a complete wet return?

    Regarding the near boiler piping, I gather from the pictures that the drop header will aid the separation of any water droplets (heavier) from the steam (lighter)further ensuring 98% quality steam. Is any pitch necessay as steam and condensate flow in the same direction and considering the short distance involved? Moreover I could not see any drop header offsets: I presume that the inverted "U"s allow for thermal expansion between risers, header, and boiler sections; right? Considering that my boiler is a Utica PEG series as in the 2nd picture, I will mimic such near boiler piping arrangement.

    In my application, calculated steam velocity with two 2" risers to header is about 12.3 ft/sec. Manufacturer recommended header size (reading between the lines - Manufacturer minimum recommended header size) is 2" which will double the steam velocity to 24.6 ft/sec. Using a 2-1/2" header steam velocity will be 17.29 ft/sec and a 3" header will yield 11.19 ft/sec. Which one would you use?

    A further detail that I reasoned is that the connection to the system, between end of header and equalizer, shall match the header size as to maintain the same steam speed throughout. Correct?

    How should I connect the system? I was planning on the following:

    On left hand side of boiler

    Provide 2"x2"x2" skimming tee to 2" riser (sized as required to obtain 24" minimum to center of sight glass) to 2" 90 to 2" nipple (sized so that header lines with wet return) to 2"x3" 90 to left hand side of 3" header.

    On the right hand side of boiler

    Install 2" 90 to 2" riser sized as required to obtain 24" minimum to center of sight glass) to 2" 90 to 2" nipple to 3"x2"x3" tee. Header will span between 2"x3" 90 on the left hand side of boiler and aforesaid tee. Using 3" close nipples install two 3"x2"x3" tees for two 2" connections to system. Provide 3"x2" reducing concentric 90 to 2" equalizer, hartford loop, etc.

    I will try to post a detail. Thanking in advance for yor time.

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