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draining/filling when radiators have TRV

Nom_Deplume Member Posts: 91
Probably a stupid question, but this summer I had to drain and then refill my hot water heating system. Since it was warm, all the TRVs were off.   But what happened to the water in the supply pipes? With the TRVs closed, I couldn't bleed or refill those sections.

I suppose they can drain out by bubbling/gurgling out, but after refilling, do I have air in there?

To be very explicit, consider an upward section of supply pipe ending in a TRV. How do I refill those pipes when the weather is so warm that the TRV is closed even at its highest setting?


  • Remove the head.

    If you remove the thermostatic head off the valve, it will allow the stem to extend out, opening the valve.

    There is usually an allan setscrew that secures the head. Others are removed by just pulling them off.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
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