Air in the hot water coil

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Hi,
I have an old back boiler, which is working ok, but every couple of years, the hot water loop gets air in it and the hot water slowly stops getting hot.

Because of the original poor fitting of the heating system any bubbles have to work their way up, through the overflow pipe into the tank.

I have a car oil removal pump, that I use for pulling out the bubbles, which I did yesterday. I don't know where the air is getting in.

When I took the top off the tank, there was a thick film of jelly like gunk, that I scraped off, I presume it's inhibitor. Here's a photo:

What is the film?
Cheers, Camerart.
 

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Havent a clue what that is but it needs sorting shouldnt be like that
 
1. Don't know what the film actually is, but its pretty typical of what you get in most F&E tanks over a period. Its the reason for emptying and cleaning the F&E before draining the system, otherwise all that muck ends up in the pipework and radiators, and possibly the boiler!
2. If you post a picture of the hot water cylinder, we might be able to advise how easy it might be to fit a bleed valve (manual or automatic) to the cylinder primary coil connections to obviate the air or at least make it easier to remove.
 
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Hi,
Here's a photo. You can see tissue, from when it leaked after I took it all out to clean. I suppose I could change the top elbow into the tank, and add a 'T' but after a life of house repairs, and I should replace the 1986 boiler, I prefer to bodge the job, until me or the boiler pack in. I only need to 'air' it every 3 ish years.

Do I need to add more inhibitor?

I'll ask the plumbers merchant where I bought the inhibitor, what the gunk is.
Thanks, C.
 

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Don't know what the film actually is, but its pretty typical of what you get in most F&E tanks over a period.
I must have led a sheltered plumbing life..Never seen anything resembling a stone of liver in any tanks.
 
The jelly is biofilm, in this case less of a film and more of a slab. After cleaning out the tank add Fernox AF 10 and you’ll be sure never to see any ever again.
 
Nothing wrong I suspect with the original fitting of the system, the issue is, with lack of maintenance. That gunge is a result of the quality of the water in the system, and I would safely bet that isn't air you're getting out, it's hydrogen. It is precisely the job of the inhibitor to prevent the system getting gunged up, highly unlikely you have got any in there!

I would suggest a full drain and flush of the system for starters, chuck a bottle of Sentinel X400 in and let that circulate for a week or 2, drain and refill a couple of times until the water runs fairly clear. Taking rads off and hosing them through wont hurt either.

Refill system, if you're happy there are no leaks, add a bottle of Sentinel X100 and leave it in there!
 
Nothing wrong I suspect with the original fitting of the system, the issue is, with lack of maintenance. That gunge is a result of the quality of the water in the system, and I would safely bet that isn't air you're getting out, it's hydrogen. It is precisely the job of the inhibitor to prevent the system getting gunged up, highly unlikely you have got any in there!

I would suggest a full drain and flush of the system for starters, chuck a bottle of Sentinel X400 in and let that circulate for a week or 2, drain and refill a couple of times until the water runs fairly clear. Taking rads off and hosing them through wont hurt either.

Refill system, if you're happy there are no leaks, add a bottle of Sentinel X100 and leave it in there!
Hi H,
About 3 years ago, the boiler clattered, so as mentioned, I took the tank out, flushed the system out with chemical, which took days, this improved things, so I did it completely again. It was clean. I added plenty of inhibitor. Afterwards no clatteriing and all radiators and water was hot.

My inexperienced thoughts are: either there is a leak, but no external signs. (Previously, I lagged the pipe work under the floor boards) It could be gas, but I think any gas should work it's way up and out, if fitted properly.
C.
 
The jelly is biofilm, in this case less of a film and more of a slab. After cleaning out the tank add Fernox AF 10 and you’ll be sure never to see any ever again.
Hi S,
As I used Sentinel previously, with the above result, this time I'll try Fernox this time (I've used Fernox before and it worked fine)
So, I'll order Fernox AF 10, and see what happens.

Thanks to all, C.
 
Hi S,
As I used Sentinel previously, with the above result, this time I'll try Fernox this time (I've used Fernox before and it worked fine)
So, I'll order Fernox AF 10, and see what happens.

Thanks to all, C.

AF10 isn’t an inhibitor.

No need to drain down, leave Sentinel in system. Just bail out and clean the feed tank then dump the AF10 in before refilling.
 

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