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Replacing large gravity system piping with smaller piping when a circulator is added

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Tom_62
Tom_62 Member Posts: 8
in Radiant Heating
My 100 year old house has large 3" (maybe 4") horizontal pipes in the basement that feed the hot water two-pipe system. A circulator was added years ago and the relatively new boiler connects to these large pipes with 1" copper. Is it possible to replace the large horizontals with something smaller to gain some head space? My neighbor replaced his huge piping with ¾" flexible PEX of all things and has experienced no problem for the last several winters. I'd like to do something similar, but it's not exactly a reversible decision.

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  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,544
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    Yes you can down size the piping. You need to gather the radiator sizes and size the piping correctly for it to work. If you only do part of the job or just some sections you could end up with balancing issues
  • Steamhead
    Steamhead Member Posts: 16,843
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    If you do this, and you later want the system to be able to circulate by gravity, it won't.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
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    icesailor
  • icesailor
    icesailor Member Posts: 7,265
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    Open the flow checks on a pumped system and forget to close them. Within 24 hours, the boiler and system will reach an equilibrium and the whole house will be hot without any assistance from any pump.

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