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Adding water to Prestige Solo 110 boiler

I need to add water to get my psi up from 9 on my tankless after bleeding the radiators but the manual says not to add cold water to a hot system.
 How long do I need to shut the system off to cool down enough to be safe ?


  • Zman
    Zman Member Posts: 7,328
    If you are careful you can slowly add at almost any temp as long as it is circulating. If you want to be very safe, I would think anything below 120 would work.
    The real danger is adding water to a dry boiler that is firing (red hot). That is how a boiler ends up a couple towns over. :o
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein