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Old House w boiler/radiators + new radiant system ... questions

RobbA
RobbA Member Posts: 2
Wow what a terrific site! Such a wealth of knowledge here.

I have a 110 year old 3 story (plus basement) house with what I believe to be it's second boiler, which is a cast iron Slant/Fin. I recently added a new floor radiant heat system using PEX on the first floor that is fed from the same boiler, but have it stepped down appropriately with mixing valves. So my complete system has just about every material in it - iron pipes, old radiators (bronze?), copper pipes, and PEX tubing.

I need to temporarily remove two of the large & heavy radiators on the 1st floor for some remodeling work. I can completely close off the new PEX radiant system, but I'm fairly certain I'll need to empty the 'legacy' system in order to remove the two radiators as they only have one valve on one side of the radiator, and no way to close off the pipes feeding them.

When bleeding the system I notice there is oil in the water, which I assume was put in to mitigate corrosion? Assuming I need to empty the system to remove the two radiators then what do I add back into the system, and at what quantity/ratio, etc.? Also, are there any issues with compatibility of the mix of materials my whole system has now? (iron, copper and PEX).

Thanks in advance for any insights on this!

Comments

  • SWEI
    SWEI Member Posts: 7,356
    RobbA said:

    When bleeding the system I notice there is oil in the water, which I assume was put in to mitigate corrosion?

    How much oil are we talking about here? Oil will not do anything to prevent corrosion, and is almost certainly not supposed to be in there.
    are there any issues with compatibility of the mix of materials my whole system has now? (iron, copper and PEX)
    As long as it's oxygen barrier PEX and the system is tight, you should not have issues. A bit of water treatment would be advisable, since the oxygen barrier is not 100% effective at preventing ingress over long periods of time.

    Can you read the marking on some of that PEX?
  • 4Johnpipe
    4Johnpipe Member Posts: 479
    What you think is oil may be remnants of boiler water additive. Hoping boiler protection piping (to prevent condensing with low / cool water return protection was installed at the time radiant was added. Would also recommend a dirt magnet device such as Caleffi or Fernox to contain metal from circulating through Pex tubing. Erosion corrosion is possible without.
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  • RobbA
    RobbA Member Posts: 2
    Thanks so much for the feedback.

    Regarding what I thought was oil - after closer inspection it appears that the water is not so much oily as it is 'dirty', and has an oil smell to it, but looking at it in a glass jar it doesn't appear to have oil mixed in.

    The Pex tubing is 7/8" oxygen barrier spec (a royal PITA to install - seriously the worst job ever).

    Anyway, it sounds like i have no worries and can drain the whole legacy system to remove the radiators. Is there anything else I should be aware of? Do I only need to open the valves on the top floor, or should I open every valve at every radiator to completely empty the system? Can i use a compressor at low pressure to 'blow out' and fully empty the system? I just want to make sure that my living room isn't soaked in dirty smelly water.
  • SWEI
    SWEI Member Posts: 7,356
    RobbA said:

    The Pex tubing is 7/8" oxygen barrier spec (a royal PITA to install - seriously the worst job ever).

    Is that 7/8" OD, or 7/8" nominal size? Brand?
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