Corrosion inhibitor question.

[Mottie]

Just over a year ago we had a partial update on our heating system - a 3 bed 1960’s semi, 10 rads. We had an unvented hot water cylinder fitted and the system was converted to a sealed one, doing away with the loft tanks. Our boiler was fine so we kept that - it’s a 20 odd year old Potterton profile 60E.

When the work was done the sysem was drained, some descaler added and the system was run for a couple of weeks (we went on holiday). They then returned, drained it again and power flushed it. Corrosion inhibitor was then added. Job done.

However, since then I have had one leak from a rad valve (replaced it myself), plus three of the last remaining original 50 year old rads upstairs replaced (two leaking and just one remaining so changed that as well). I’m now decorating the landing and when I removed the landing radiator, there was evidence of a slight leak on the back of it so for what a 600x600 single rad cost, I changed that too.

Now, my question: all these rads being changed and topping up the system has obviously diluted the corrosion inhibitor. I have a 1 litre of Sentinal X100 inhibitor. Is it okay to add the whole 1 litre to the system? It won’t overdose it, will it?

 

[Nige F]

That'll be fine - crack on

 

[Mottie]

One more question on this. Since adding a can of X100, I’ve experienced kettling in the boiler and I keep getting air in one of my rads. It’s a sealed system. Is it just a co-incidence or could it be too much inhibitor in the system? Not sure what corrosion inhibitor they added last time - if not the same as I’ve added, could mixing two different types of inhibitor give this problem? Not too bothered as I’ve decided to replace the 26 year old boiler this summer anyway, just curious.

 

[muggles]

No, you can't overdose the system. You've most likely introduced some air into it when you added the inhibitor

 

[Mottie]

Thanks. That’s strange then. I bled the system no different to how I had done for the past 26 years and I’ve just gone round and bled it again including the bleed valves at the highest point (flow and return at the boiler which is in the loft).
Boiler fires up and after about 1 minute max the noise starts up (definitely in the boiler as I can feel it through the casing) and it stays there all the time it’s running. When the boiler stops/shuts down, I can hear it for about 30 seconds after the boiler and the pump has stopped.

Nothing to do with the inhibitor then, just knackered!

 

[JBR]

Good thread. Silly question, I'm sure many will say, but where do you pour in the inhibitor?

 

[Mottie]

I let some water out, removed the blanking plug from the top of my tall towel rail (highest point on the system) and poured the litre of inhibitor in there. Bled the system afterwards.

 

[WhydidIstart]

Hi, I assume you re-pressurised the system after adding the inhibitor and then again after bleeding the rads?

Does the pressure stay normal when the heating is operating, i.e. 1 – 1.5 bar ish when cold, a bit more than that when hot and then back to the same pressure again when cold?

You mentioned the boiler is in the loft (is that above your towel rail, or is that also in the loft?). Are the bleed valves on the flow and return that you mentioned above the boiler? If not, could there still be some air trapped inside the boiler?

 

[Mottie]

Yes, system repressurised and bled several times. Pressures when cold and hot same as it’s always been - between 1 and 2.5 bar. The flow and return bleeds are at the very highest point in the system. They’re just above the boiler in the loft. I only get a small amount out of them and I think they are only there to prevent air locks when filling the system. Anyway, it’s served it’s purpose for 26 years so it’s time to go!

 

[JBR]

I let some water out, removed the blanking plug from the top of my tall towel rail (highest point on the system) and poured the litre of inhibitor in there. Bled the system afterwards.

Thanks for that. My radiators are all on the same level, being a bungalow. I suppose I could close the valves on all but one radiator and drain some water. Trying to coax some inhibitor into a horizontal cap, even if I could open it, might be difficult.
I do have a Magnaclean-type filter below my boiler. I suppose it might be easier to turn both taps off, remove the water in the filter and pour some inhibitor in there. It wouldn't take much to fill it, but I could repeat the process after a few hours.

Sorry to intrude on this thread, by the way.