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hot_rod Member Posts: 21,868
typically only Di-potassium phosphate is added to RV fluids.

This is not enough protection for modern hydronic systems. RV fluid is intended to be flushed out after use, so a comprehensive inhibitor package is not required. The price reflects that, of course and there are different blends offering different freeze and burst protection levels.

Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream


  • joe_61
    joe_61 Member Posts: 21

  • hot_rod
    hot_rod Member Posts: 21,868

    check with the Weil installation manual, they usually address that.

    Be sure it is a glycol inhibited for hydronic use. Stay away from RV type of fluids :)

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Plumdog_2
    Plumdog_2 Member Posts: 873
    RV type glycol

    Would you explain, HR, once more why not to use RV type fluids. I had a homeowner wanting to pump 25 gallons into his self-installed system. One brand, on sale 2 for $7.00, is labeled "-50 burst protection" but only scales out at 15 degrees on my instrument. If I remember correctly, it will foam from the pump turbulence?
  • kpc_40
    kpc_40 Member Posts: 62
    thhe RV stuff...

    is not rated to be use in heating systems. I t has no oxygen inhibitors and will break down pretty quick.
  • Your instrurment...

    (refractometer)is telling you the freeze protection number. That is the temp at which the very first ice crystal will begin to form and start turning it into slush. Then there is flow protection, which is the temp at which it will cease to flow as a slush. Burst protection is the number at which the solution will stop contracting and begin to expand again. All glycols will contract at first as the temp drops but below a certain temp will begin to expand. What you have in your can that starts to freeze at 15* is some mixture of glycol and water not 100% glycol. Generally you can only find the 100% stuff at the higher latitudes where extreme cold can be experienced. You have to special order it in most of the lower 40 states. It always pays to check what's in the can with your instrument before adding water because, as you have discovered, it could already be at the freeze temp desired straight out of the can and adding water will dilute it further and cause you many woes, whether it be removing and adding more because you checked it afterwards and it was weak or failure of your system because you didn't check it and found out the hard way. The -50* burst protection advertised throws a lot of people off the track and sells a lot more glycol for the mfg when you have to throw away part of what's in the system and then buy and add more. I personally have a real bug up my butt over that.
  • Brad White_202
    Brad White_202 Member Posts: 105

    Automotive AF has silicates, finely ground sand, which I am told assist coating the passages and do other useful things in a car. But in a hydronic system, become an abrasive slurry. Never mind the chemistry.

    Check out Noble No-Burst. Drew at Noble has always been very helpful.
  • Drew_2
    Drew_2 Member Posts: 158

    I couldn't of said it better. Just 1 note: We have a couple of products that are 98%(Super Noburst) & 96% (Noburst HD). These are diluted by the contractor to a desired freeze Temp.
  • Thanks,

    I'll keep those products in mind if I move forward with the one I have on the table right now.

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