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Adding propylene glycol to radiant system

I have read most everything I can find on here and elsewhere about putting glycol into a radiant system. I have a few questions about the install process.

I will be installing the glycol mix through the boiler drain using a drill pump. The consensus is that the glycol mix should be added with the boiler off and the zone valves open. I have five zones and two Grundfos pumps (one circulating, one injecting). When I shut the boiler off the Grundfus pumps also shut off. When I open the drain valve with the drill pump attached (but off), water is forced back through the drill pump.

My questions are:

1. Will the drill pump be sufficient to push the glycol mixture into the system and circulate it if the Grundfos pumps are off?

2. How do I know if the zone valves are open when the system is powered off?

I live in Alaska, where we experience frequent power outages and the house will be unoccupied from November - February. Please skip the lectures about the downsides of glycol in radiant systems.


  • icesailor
    icesailor Member Posts: 7,265
    Glycol, radiant & Drill Pumps:

    Who said that you can't use Glycol in a radiant system?

    If you tried using s "Drill Pump" to inject glycol into the system, and water was being forced back through the drill  pump before you tried to pump the glycol into the system, you are lacking in the understanding of the process. You need help. If you do it as you have hinted, you will have a catastrophic event in your system at some time in the future. Do you know how much glycol to add to your system? Do you have an accurate answer as to how much water is now in your system? You need to know these things. I would find it personally difficult to use a "drill pump" to achieve what you want to do. You need the help of someone experienced and with the proper equipment.

    I'm not saying that you can't do it. I just feel that this project isn'y one to be taken lightly.

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