x400 - over-long duration

[UserError]

Hello, I put x400 in our system at the end of November, intending to leave it for a few days but took ill and it's still in there. Now on the mend I want to drain it soon & I've just emailed Sentinel who replied:

"The maximum recommended time for Sentinel X400 to be in the system prior to flushing is 4 weeks. If it has been left in longer it will not damage the system but may not have cleaned as efficiently"

To me that's worded oddly as generally things carry on reacting (till they're used up) so I then asked if the stuff lost it's effectiveness (& the sludge precipitates back out again or something) and was it therefore worth re-dosing, but got a hopeless response to that:

"That would depend on your system and its condition once the system has been flushed."
So I'll drain it, run water through till it's clear-ish and then how would anyone know whether it needed more?

I dosed it in the first place as preventative maintenance, rather than in response to any problem (I had the system drained whilst I fitted a new radiator downstairs and I also went round vibrating all the radiators with my SDS rubber hammer attachment prior to this draining)

So, humming & ha-ing as to whether to just drain it & be done, or re-dose and put everything back a while longer while it acts - I've got new TRV valves to fit on three radiators.
Thoughts?
Much obliged

 

[Chuck]

I'd just continue the drain / flush / refill / test pH / dose with inhibitor as though everything was normal. I might give it an extra flush for luck.

You will never get a reliable 'theoretical' answer to the question you are asking because it will depend on the exact details of the system and its history. If you really want to know you'll need expensive / destructive testing that will cost far more than the value of the information you'd gain.

If you are still concerned, get a decent independent heating-engineer to power flush the system for you.