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How to clean inside of Radiator

My father in-law has an outside wood boiler hooked up to a radiator (water not steam) in the shop. It works fine but not enough to warm the shop up. He has two other old radiators that are not hooked up. I would like to get them going but I am worried they are full of junk inside that I don't want recirculating through the system. I have searched but all I find are articles on how to restore the outside. What can I do to insure the insides are clean?


    HVACNUT Member Posts: 3,920
    I've heard that a tremendous shot of UV, or some other kind of very powerful light, either through the cast iron or some other way.  I've also heard of injecting disinfectant, where it knocks it out in like a minute. 

    But I personally have used this. 
    You might need to do it a few times, then follow up with an inhibitor. 
    I'll let the grownups talk now.
  • kcopp
    kcopp Member Posts: 3,732
    Best bet is to make a wand hooked up to a garden hose. I have one that is a 3/8" compression x Female hose thread. The 3/8" copper is about 30" long. the end is crimped down and I drilled about a dozen 1/8" holes along the sides for about 8". A few passes inside under pressure will get a lot of junk to wash out.
  • psb75
    psb75 Member Posts: 369
    I wouldn't worry too much about cleaning the inside of a cast iron radiator. Yes they are rusty inside. Flush them out well with fast moving water. Fill and drain a couple of times. Use a cleaner if you want like Hercules. In the end they will still have some light rust in the boiler water. Really heavy particulates usually settle in the bottom concavities of the radiator. Put a magnetic dirt separator on your system. Then call those rads "good to go." By the way, that outdoor wood boiler will create PLENTY of its own rust.
  • jeffreybandel
    jeffreybandel Member Posts: 3
    OK. Is it just a matter of hooking up a hose (or a copper manifold cleaner like kcopp suggested) to the bottom port on one side and letting it run out the bottom port of the other side.
  • hot_rod
    hot_rod Member Posts: 14,797
    Also, add a good dirt and particle separator to keep chunks out of pumps valves, etc.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • jeffreybandel
    jeffreybandel Member Posts: 3
    OK. I suspect it should be installed on the return side?
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