Keep getting air in radiator

[Alfie25]

I've got a fully pumped open vented system and keep getting air in one downstairs double radiator. I can hear it gurgling away when the heating is on and so frequently have to bleed it. I also (but less frequently) have to bleed my magnaclean which is towards the top of the system (and on the HW circuit (I know this isn't the ideal location but I inherited the system and I guess when HW and CH are on together that the water gets fully pumped through the magnaclean)

My pump setting is on 2. The system was fully drained 3 months ago when 2 radiators were replaced. Could it still be the fresh water releasing its oxygen? I would have thought over 3 months it would have finished that by now, although I've predominantly had the HW on recently but not the CH on with it being summer.

 

[Boilerman2]

When the system was refilled, did you add Corrosion Inhibitor to the water? if not WHY NOT!! get some Fernox F.1 and add to the circulating water this whould stop the build up of air/Hydrogen in the Radiator

 

[silverback]

You either have ingress of air somewhere or major corrosion occurring in the system which is causing the air, either way there is something wrong with your system and you should get it looked at

 

[Alfie25]

I can't see how it's major corrosion as the water coming out is very clear. The feed and expansion tank is working fine and again the water in that is clear.

How can you detect where air is being drawn into the system?

 

[silverback]

the air has to be coming from somewhere, it cannot just generate from the water, once water has released its free oxygen it has no more to give, air means either it is been drawn in, or corrosion is taking place in the system which is causing the air build up, as your system is open vented you need to have a look at your cold feed and open vent arrangement, where does it connect into the system

 

[silverback]

did you use to have this problem before you had the two radiators replaced

 

[Alfie25]

Hard to say as I'd just moved in but I don't think the noise was present beforehand.

The pump makes a noise as if it has air in it but I've bled it using the bleed screw on the front and there's no air in it. After it's being going a while and the water gets hot the pump makes a bubbling sound, which made me wonder if the pump itself could be generating bubbles. Prior to replacing the radiators it was on speed 3 but I turned it down to 2 as it was noisier on 3 and works ok on 2.

Cold feed is from the F/E tank in the loft, no blockages as water can get into the system fine. The vent pipe is over the cold water storage tank, not the F/E tank. It seems to have been set up this way for a long time, so I can't see why the layout would suddenly be an issue.

 

[silverback]

So you have 2 vents over your cold water storage tank, not good having your heating vent over your cold water storage tank, if it pumps over heating water will be emptied into the tank from where you use the water for bathing and brushing your teeth, if you only have one vent over the cold water storage tank and no vent over the heating F&E tank, this would suggest that you have a combined feed and vent from your F&E tank

 

[Alfie25]

Hi, I started a separate post with a separate (but probably linked) problem.

Silverback, in reply to your last question, I only have one vent pipe, and it's over the big cold water tank. There is no vent pipe over the small f/e tank.

I did think it looked strange cos like you say, with it pumping over, the water from the CH circuit is going into the HW supply (the cold water tank doesn't feed any cold water supply at all - it's just for the HW). Can you tell me more about these combined feed and vent systems.

EDIT - After reading more on the subject it would appear I do indeed have a combined Feed and Vent pipe. I'm still getting air in my system though!

 

[Alfie25]

Just coming back to this thread, my problems with 'air' in the system continue. I thought I'd leave it a couple of months and see if it was just air in the new water working its way out but it isn't. Every 2 to 4 weeks I'm bleeding a small amount from the magnaclean. Last time I released the air from the magnaclean into an upturned glass then stuck a match to it. I got a little 'whoosh' so I'm assuming it is hydrogen.

So... can I just put some corrosion inhibitor in the system, or will it need a 'cleanser' in it first of all? If so, then what's a decent but mild cleanser? I'm reluctant to put anything too harsh in it as I know there've been micro leaks in the past (telltale was an empty bottle of leak sealer I found in the loft!) so I'm worried a system cleanser may lead to the leaks returning.

 

[45yearsagasman]

The hydrogen is a by product of a chemical reaction in your system(corrosion). Add some more inhibitor to your system, preferably via the Magnaclean or a rad. Fernox F1 or Sentinel X100.

 

[Alfie25]

Thanks - so you're saying no need to add a cleaner to the system, just some corrosion inhibitor? What I'm planning to do is to remove the magnaclean lid and add it that way - do you know how much volume the magnaclean takes? I see Fernox F1 comes in 500ml bottle. Will this all go in or should I go for the superconcentrate stuff you get in a tube.

 

[45yearsagasman]

If the water is clear and you have no circulation problems the a cleaner is not necessary at all. Your Magnaclean should be doing its job. Put the whole 500ml in. I have no idea how much the magna chamber holds. You may have to perform the operation twice, no problems with that. I always use the liquid.

 

[Alfie25]

Ok, I'll give it a go. I'm new to all this having never owned a house before and I've read a few stories about magnaclean isolation valves leaking afterwards. Assuming the worst and the magnaclean valves start leaking after I turn them back on, am I stuck? I'd get a plumber in to repair but what to do in the meantime? I've got an open vent system so could isolate the feed tank, and the magnaclean is towards the top of the system so presumably if it leaks it shouldn't take too long for the water level to drop below the magnaclean?? There's only the towel rail in the bathroom that's higher up.

Or if they leak, do they tend to leak slowly?