How clean should CH be after flushing?

[shd1970]

As explained above...
Your version of flushing is like running bath taps, with the plug removed, to get rid of the scum halfway up the bath sides.

Is it though as i’m filling the system each time, bleeding all rads so the system is completely full and at 1bar, run the system to slosh around and dilute and then drain
Not the quickest method but it has to be removing albeit slowly

 

[shd1970]

Fernox have a water quality test where you send off a sample. I don't know whether this would identify what the colour is due to. No doubt other services are available.

My earlier unanswered question about what the cleaner's instructions say was supposed to suggest "does the colour matter?", i.e. if you've used the cleaner according to its instructions then the system "must now be clean", or "clean enough that you don't need to worry about the remaining discolouration". Personally when I recently cleaned my system I put the drain hose down the drain and didn't look at the colour. I'm not sure what I think about this, what do the pros reckon?

One thought, when you drain are you opening all the bleed valves on the radiators?

Apologies for forgetting to respond @endecotp

Yes when I drain I open the upstairs bleed valves to break the vacuum on the system

Here are the instructions from the back of the bottle which do not mention about the colour of the fluid after removal