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Should I flush my hot water radiant system occasionally?

HansonGHansonG Member Posts: 3
Hi- I've got a self-installed (with a bit of pro engineering in the beginning) radiant system with a Burnham RV3 cast iron boiler and 2 Grundfos pumps pushing (?pulling!) hot water through 3 radiators and 2 lower temp zone areas plus a concrete slab in one area and tubing over subfloor in another. The system has needed maintenance items- valve motors, 1 noisy pump replacement, a boiler controller over about 15 years but hasn't had a leak or plumbing issues during this time. It's only been "opened up" about 4 or 5 times with the open areas limited by isolation valves for the most part. With the advice of a couple of really great suppliers and online information, I've done all the maintenance myself. I've never had a "pro" look at this system. I clean the firebox fairly regularly but as far as I can tell, nothing else has been needed. I still have this nagging feeling I should clear that black stuff from the system and get fresh (distilled or deionized?) put back in. Anyone have a take on this question? Any help would be appreciated.


  • mattmia2mattmia2 Member Posts: 1,186
    No. The oxygen in the fresh water will make new black stuff with the metals in the system.
  • GroundUpGroundUp Member Posts: 960
    15 years is about due for a flush IMO, but if the water chemistry is still in spec it's not a necessity. The thing with radiant is the fluid velocity is typically pretty low which allows any sediment or particulate matter to settle in it and plug up the tubing. If the water is black anywhere, it's time for a flush.
  • fenkelfenkel Member Posts: 80
    I'd rise the sytem out, clean with rohmor 9100, rinse and then.use rohmar 922, i would use deminerized water, but make sure you have deminerized makeup water for autofill.. then, every year send in a sample to rohmar for a chemical evaluation..youll never have an issue after this..sentinel is a good choice as well for boiler cleaners and conditioners
    Id also have your burners inspected/ cleaned and a gas/ Combustion done every two years..
    Also inspect the exhaust venting for rust..
  • ZmanZman Member Posts: 5,736
    Does your tubing have an O2 barrier? Does the system leak? Have you checked the water PH and TDS?
    The sediment in the water is often a sign of O2 ingress. The answer to your question depends on those 3 questions.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • jumperjumper Member Posts: 1,430
    Why are sidestream filters so rare?
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