The constant need to bleed conundrum!!

[Slime]

Hi all
I can't find an definitive answer so I'll tell you my story.
The bathroom radiator/towel heater is constantly having to be bled, say, every couple of weeks.
I have a combi boiler but I almost never have to 'top it up', it's as if the system is making it's own air.
That makes me think there's a chemical reaction going on somewhere in my system, most of the rads being about fifteen years old.
Someone said it merely needs some inhibitor, if that's the case, is there a particularly recommended one.
If that's not that case, any other thoughts.

Thanks in advance,
Slime.

 

[Harry Bloomfield]

Someone said it merely needs some inhibitor, if that's the case, is there a particularly recommended one.

Possibly - When you bleed it, catch some of the gas which comes out, then try igniting it. If it pops, it's hydrogen,
generated inside your system, as a result of the radiators rusting internally. The rusting process, takes up the O of H2O, leaving the H, hydrogen.

Hydrogen, is lighter than air, so use an upturned container, when trying to catch it.

 

[Dereekoo]

Fernox F1 or Sentinel X100 seems to be the go to ones, at £15-20 it hardly worth not doing and see what happens

 

[CountryFan]

I’ve used Calchem previously and it seems good. As for the constant need to bleed, then it does sound like hydrogen as per @Harry Bloomfield. It seems odd to me that you’re not topping the boiler up frequently. You can also bleed some system water in an unused jam jar, add some nails and leave them for 3 days, if they go rusty the that’s what’s happening inside your heating system.

 

[Hugh Jaleak]

Likely to be Hydrogen, the mixture of metals within the system, and the water acting as the Electrolyte allows corrosion to take place, by products of which are Hydrogen and black magnetite sludge. Might be worth draining some water out, putting some Sentinel X400 cleaner for a few weeks, before draining the lot out, flush through best you can with clean water, then chuck some X100 or Fernox in.


That should prevent any more corrosion hopefully, don't forget to top the Inhibitor up again if you drain the system in future for any reason.