Reality of not using cleaner after installing new radiators in a clean system

12 Oct 2016
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United Kingdom
Regarding: Clean sealed central heating system, powerflushed and inhibitor added a few years ago and system water still remains clear as tap water.
Question: After cleanly installing a few brand new radiators with no flux, in reality is cleaner really required before fully flushing the system down a few times with tap water?
If so why? There might be a bit of manufacturing oils in the radiators but wouldn't a few cold water flushes be safer than introducing cleaner?
If the new radiators are not clean using a cleaning solution, what are the potential problems?
From what I understand, adding cleaner can introduce problems itself if not removed thoroughly after ie, the TDS level in the system taken down to the same level of tap water by flushing before adding inhibitor.
Last edited:
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Strictly speaking you are supposed to flush system after adding a new radiator. I don’t think a mild cleaning chemical will do any harm . especially if you flush system thoroughly. Some of the chemicals neutralise if left in system I am told, although I would advise fully flushing it. Always flush system when water is still warm in it.
The potential oils left inside new radiators would be a risk to any plastic pipes and plastic fittings on a heating system, but otherwise I doubt if they cause any problems.
I never flush systems when I replace a radiator. If I did, it would add greatly to labour.

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