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Boiler System Cleaning Agents - Which One?

BigRob Member Posts: 322
Background:  Our condo building hydronic heating system was essentially neglected for 10 years before I came around.  About a year ago our Ergomax reverse indirect and cast iron boiler were replaced as they were in pretty bad shape. 

Our 5 wall radiators never worked well and the contractors essentially gave up.  I started poking around and did some head loss math: the tubes to the radiators (which are on the bottom floor of 3) had to be clogged.  Three quarters of a bucket full of iron oxide later I was getting good flow.  I flushed the system.  That was about 6 months ago. 

Last weekend I checked the wye strainer and hydro seperator.  There was a bit of flakes and sand (mainly iron oxide, I believe).  Our 12 radiant floors (about 10k BTU/h each) are flowing.  It's unknown if any iron oxide are in the floors.  I scanned 4 of the floors (2 on level 2 and 2 on level 3) with an IR camera and there did not appear to be any blockages.  The hydronic piping is copper and pex, brass fittings and valves, stainless boiler HX, iron pumps, and no iron pipe.

Based on calculated pressure drops, I believe there is significant scale in the radiator distribution piping, and there is probably iron oxide pooled in spots.

TSP seems like a decent option, as well as chelating agents.  I've seem the Rhomar products.  Can you please give me your thoughts on the best treatment strategy and products?

If I could safely dissolve the iron oxide and scale, then flush, that would be awesome.  I'm done with the air compressor and water hose method!


  • BigRob
    BigRob Member Posts: 322
    I forgot to mention..

    When I unclogged the radiator lines, there was a thin, black tar like layer that fouled our Rehau mainfold flowmeters.  I assumed it was fine iron oxide at the time - not so sure now.  I was able to clean it off, and when I did it would flake, then disolved with water.
  • hot_rod
    hot_rod Member Posts: 21,876
    does it stick to a magnet

    the sludge that comes out. Is it non barrier pex? What operating temperature?

    I have had excellent luck with Rhomar products. I believe you can send them a fluid sample to determine what is going on inside them pipes. Something is causing that sludge.

    It could also be a bacteria, and soap based cleaners will not correct that.

    It is best to determine what the problem is caused by before dumping hundreds of dollars worth of chemicals and hours of labor into the job.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • M Lane
    M Lane Member Posts: 123

    See if you can find a dealer. Aside from different chemicals, they have an elaborate pump/flush/magnet system you can rent.
  • BigRob
    BigRob Member Posts: 322

    The "sand" that came out does stick to a magnet. Al least it looks like sand now that it's dry. In terms of a sludge, there may have been finer particles that when wet look sludgy. When I check the wye stainer last weekend the water was clear, although there was some sand and bigger flakes in the wye strainer. I'm pretty sure it was residuaI from the old boiler and/or ergomax corrosion. I have half bucket of the iron oxide sand in the garage.

    The pex say oxygaurd, so I assume it does have an oxygen barrier..?

    Ron, off topic, but do you know of similar products like these in the US:


    I need to fix up a hot water recirculation system.
  • BigRob
    BigRob Member Posts: 322

    That injector/filter thing is pretty sweet