Added Inhibitor but still getting hydrogen in radiators.

John R · 9 Mar 2021

Hello All,

First time poster - really hoping to get some pointers of what to do next with this problem.

The problem started when we did our bathroom and installed a new towel rail.

I found I was having to bleed the highest radiator in the house every few days - working fine and still hot but the bubbling noise was really annoying.
Long story short I eventually established this was hydrogen by lighting the gas as I bled it!

I know there was no inhibitor in the system so some Fernox F1 was added after leaving F3 cleaner in the system for a week. The engineer said the water actually looked pretty clean when it was removed.

Anyhow this was 3 weeks ago and it has not helped. Gas is still gathering in the radiator at the same pace.

The other radiators in the house are about 17 years old. Some have some minor corrosion / paint flaking but looks to be on the outside (if its possible to tell??)

Been advised to try replacing them which am happy to do but obviously want to be reasonably sure that will solve the problem.

Any ideas / guidance would be much appreciated. Thanks in advance!

ianmcd · 9 Mar 2021

If it is definately hydrogen, inhibitor wont make any difference you need Sentinell X700 Biocide or Fernox equivalent, the Hydrogen is produced by Bacteria present in the system water, this bacteria needs to be neutralised

John R · 9 Mar 2021

ianmcd said:
If it is definately hydrogen, inhibitor wont make any difference you need Sentinell X700 Biocide or Fernox equivalent, the Hydrogen is produced by Bacteria present in the system water, this bacteria needs to be neutralised

Thanks for the reply.
I questioned this with Fernox. They said that the F1 was the correct product and 'Biocide is normally only used if you have just underfloor heating or you have a bacterial infection in the F & E tank.'
(FYI mine is a combi boiler system)

JohnD · 9 Mar 2021

ianmcd said:
If it is definately hydrogen, inhibitor wont make any difference

are you sure?

when iron combines with water to form rust or magnetite, what is the other product?

sxturbo · 9 Mar 2021

It should be noted that hydrogen bonds less strongly to oxygen than iron does. This means that iron will, albeit slowly, take the oxygen right out of water to become rust - producing hydrogen gas

You will probably have to give it a bit of time for the inhibitor to work.

I've got a de-airater in my system which removes the oxygen from the water. I don't have inhibitor either mine is just filled with softened water,

John R · 9 Mar 2021

sxturbo said:
It should be noted that hydrogen bonds less strongly to oxygen than iron does. This means that iron will, albeit slowly, take the oxygen right out of water to become rust - producing hydrogen gas

You will probably have to give it a bit of time for the inhibitor to work.

I've got a de-airater in my system which removes the oxygen from the water. I don't have inhibitor either mine is just filled with softened water,

Thanks ill guess ill give it a bit longer and see how it goes...

Funny how doing the bathroom triggered it off - would it be the new radiator that is giving off the gas then? Anyone have any thoughts on that? - just curious.

Madrab · 9 Mar 2021

Get some litmus paper, do a test on your system and see if it is overly alkaline/acidic. If the system is over alkaline/acidic, cleaner type dependent, if it's not flushed or neutralised properly it will start to eat the ally and create hydrogen in the process.

What boiler do you have? Does it have an ally HEX?

Inhibitor is PH neutral, so it won't actually adjust the PH by much unless you used large amounts. It needs drained and flushed or use a neutraliser.

John R · 9 Mar 2021

Madrab said:
Get some litmus paper, do a test on your system and see if it is overly alkaline/acidic. If the system is over alkaline/acidic, dependent on the cleaners used, if it's not flushed or neutralised properly, it will start to eat the ally and create hydrogen in the process.

What boiler do you have? Does it have an ally HEX?

Inhibitor is PH neutral, so it won't actually adjust the PH by much unless you used large amounts. It needs drained and flushed or use a neutraliser.

It a Worcester Bosch Cdi

What is an ally HEX? (Sorry my knowledge on this stuff is very limited)

sxturbo · 9 Mar 2021

John R said:
It a Worcester Bosch Cdi

What is an ally HEX? (Sorry my knowledge on this stuff is very limited)

Aluminium heat exchanger

Madrab · 10 Mar 2021

As mentioned, Aluminium Alloy Heat Exchanger .... Which a lot of the CDI's have. It may not be but it doesn't cost much to buy a book of litmus paper and it's an instant test. Is the system water isn't close to PH Neutral it can start to dissolve the aluminium.

John R · 10 Mar 2021

Madrab said:
As mentioned, Aluminium Alloy Heat Exchanger .... Which a lot of the CDI's have. It may not be but it doesn't cost much to buy a book of litmus paper and it's an instant test. Is the system water isn't close to PH Neutral it can start to dissolve the aluminium.

Thanks - got to be worth a go for a price of the paper - even just to eliminate it as a possibility.

The British Gas boiler service is due next month - would they be able to see visually if there is any corrosion to the heat exchanger?

sxturbo · 10 Mar 2021

John R said:
Thanks - got to be worth a go for a price of the paper - even just to eliminate it as a possibility.

The British Gas boiler service is due next month - would they be able to see visually if there is any corrosion to the heat exchanger?

In theory if they do a proper service yes. But BG don't, they just do a flue analysis and check for leaks they'll be all done in 30 minutes

Celeronmanuk · 10 Mar 2021

I was getting hydrogen build up in a new install, confirmed by collecting and igniting! Ran sentinel cleaner (can't remember which one) through it, refilled and drained a few times, then fill with inhibitor and fine ever since.

John R · 10 Mar 2021

Celeronmanuk said:
I was getting hydrogen build up in a new install, confirmed by collecting and igniting! Ran sentinel cleaner (can't remember which one) through it, refilled and drained a few times, then fill with inhibitor and fine ever since.

Did the inhibitor work straight away or did you have to wait a while?

Celeronmanuk · 10 Mar 2021

John R said:
Did the inhibitor work straight away or did you have to wait a while?

I did all that work over a few days which involved lots of bleeding, so can't be sure at which point the hydrogen stopped. But I haven't had a problem since. I'm guessing the installer didn't clean the system properly. It was a Worcester combi btw, so aluminium heat exchanger.

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Added Inhibitor but still getting hydrogen in radiators.

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