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Main sizing?

malp Member Posts: 27
First off, a big thank you to Dan and all the helpful people on this site. Without you all, I'd be using space heaters now. I bought a house with steam heat. First time I turned on the heat, the pipes banged. I turned the heat off and made sure nothing had burst. I read the lost art of steam and then started tracing pipes. One of the risers was sloped straight down to get around an obstruction. The riser led to an enclosed porch. The radiator there had filled with water and cracked open. The previous owners had kept the heat running anyway, so the porch became a sauna. The paint was peeling and the carpet smelled. The previous owners switched to space heaters after that, which kept the pipes from bursting, but they must have been freezing. Their bedroom walls were stained with condensation. The other pipes were pitched correctly, but some of them had been replaced with 1/2-inch copper. Those radiators made sloshing noises but not much else. So I followed Dan's charts on pipe and valve sizes and repiped and repiped and repiped. I ordered some 2.5-in pipe and fittings and redid the boiler to the manufactures spec. Now everything heats beautifully. Interestingly, the original risers to the second floor were all sound. The only pipes with signs of rot ran horizontally.

Finally, the question: The mains are only 1.5-inch pipe. One main has 184 sq ft edr hooked up to it including exposed uninsulated risers. The second main has 91 sq ft edr hooked up to it. Do I need to repipe the mains with 2-inch pipe? Dan's chart only lists 2-inch pipe and up. If need be, I could move one of the radiators to the less-loaded main, so mains would feed 139 sq ft edr and 136 sq ft edr.

Again thank you. Without your wonderful advice, I'd still be using oily pipe dope, wishing I knew of drop headers, and cursing winter.


  • Steamhead
    Steamhead Member Posts: 15,657
    We see plenty of 1-1/2" mains

    in little Baltimore rowhouses, and they work fine if you don't put too much load on them. I would say as long as they work, no need to change anything. 
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • malp
    malp Member Posts: 27
    thank you

    Thank you! I was just concerned because I'm about to order insulation ($$$$) for the mains.
  • Insulation

    You'll be pleasantly surprised how much difference the insulation will make.
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