Air in CH system...but why?

It will continue to need bleeding for around a year, as the air comes out of the system and collects in one radiator. In my system, it always collect the last of the air in the bathroom radiator - the one nearest the pump.
 
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The manual vents would need bleeding several times until the system is up and running....the AAVs will either leak or block.
 
Thank you. We had a similar situation about four years ago after a local plumber fitted a new radiator in the bathroom. The boiler worked but was extremely noisy, making a rushing, gurgling sound during operation. He told me the air would work itself out of the system but it didn't, and having had combis in our previous two houses I wasn't sufficiently familiar with conventional systems to be able to argue about it.

The noise persisted for several weeks, so I called the plumber to try to get him to revisit and deal with the situation, but it proved impossible to pin him down. So I did some research, including probably on this forum, then fitted the original AAVs myself and after a period of weeks all the air was gone.
 
For future reference, I believe you misinterpreted the instructions for the inhibitor, and you drained the whole system when draining just a litre would have sufficed. And if you did intend to fully drain the system, that would have been better achieved by opening the radiator air vents.

Hindsight over, now what to do....

1. You have a Magneclean. Have you given that a full clean, not just an in-situ flush?
2. You say you may have flushed gunge from the F&E tank into the system. Have you inspected and cleaned the pump impellor? Many are rendered almost useless with debris blocking it. To do this you must isolate the pump (via its local valves), take the pump head off, and use a piece of soft wire (I find twin and earth cable earth wire is good for this) to prod out each 'slot' of the impellor. Are you competant to do this?
3. Once the pump is working properly it'll both move the trapped air to the bleed points more effectively and also move sediment (gunge) too, so a second flush of the Magneclean and a second pump inspection is advised in a week.
4. Beyond that a quick clean of the Magneclean 3 months later should suffice (more frequently if significant quantities of gunge are found).
 
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For future reference, I believe you misinterpreted the instructions for the inhibitor, and you drained the whole system when draining just a litre would have sufficed. And if you did intend to fully drain the system, that would have been better achieved by opening the radiator air vents.

Hindsight over, now what to do....

1. You have a Magneclean. Have you given that a full clean, not just an in-situ flush?
2. You say you may have flushed gunge from the F&E tank into the system. Have you inspected and cleaned the pump impellor? Many are rendered almost useless with debris blocking it. To do this you must isolate the pump (via its local valves), take the pump head off, and use a piece of soft wire (I find twin and earth cable earth wire is good for this) to prod out each 'slot' of the impellor. Are you competant to do this?
3. Once the pump is working properly it'll both move the trapped air to the bleed points more effectively and also move sediment (gunge) too, so a second flush of the Magneclean and a second pump inspection is advised in a week.
4. Beyond that a quick clean of the Magneclean 3 months later should suffice (more frequently if significant quantities of gunge are found).

Yes, with hindsight you’re right and I didn’t need to drain the entire system, though in my scant defence I was following instructions on a YouTube clip.

I’m certainly not competent enough to disassemble and service/ clean the pump, but in any case I believe that the system is now almost free of air and that the AAV and occasional bleeding of the rads will remove the rest. If there is gunge in there then I can only hope that a) it flushes out with the passage of time or b) my service contract takes care of the cost of any future failure of the pump or deterioration in performance.

As for the Magnaclean, whilst early models were, I believe prone to leaking if taken apart, mine is a later one and I reckon it’s safe to give your advice on that score a whirl. Many thanks.
 

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