Air trapped in the radiators

[Someuser08]

I've been having a long standing problem with a couple of radiators in my house that I never got round to fixing. Basically when valves are opened fully it sounds like really loud running water. I've bled them obviously many times (with no air coming out of them) with no results. I reduced the flow and managed to get the sounds to an acceptable level, but obviously this reduces heating efficiency and I really want to have it solved for at least one of them (in the bathroom).

It occurred to me recently that both troubled radiators are of the same design - vertical oval bars like this one: https://www.amazon.co.uk/dp/B01AY0U23K/ref=cm_sw_r_cp_apa_i_z6.wCbHY8BNY5
So I started thinking may be the problem is with its design? One of the radiators is also the highest radiator in the house, so most likely traps any air from the whole system as well.

Does anyone know how to bleed this type of radiator properly? I now have enough plumbing skills to attempt to completely drain the radiator down, but I'm afraid that it would need correct filling procedure anyway and in the long run if it collects air over time I don't want to be doing this all again and again.

Thanks.

 

[Someuser08]

An update - in the morning I managed to unscrew the bit opposite the bleeding valve and a bit of air did come out with a spray of water. After that the radiator sounded better, but this evening we are back to regular loud stream any ideas what to do? It literally sounds like its empty(i know its not as its hot all the way through) and small stream of water being poured into it...

 

[gasbusters]

Out of curiosity whats the pressure showing on the boiler? Do you have to regularly top up the boiler? Is the pressure constantly dropping?

Has boiler been serviced? What make and model of boiler?

Those radiators in the link seem fine.

Btw what type of system is it?

 

[Someuser08]

The combi boiler is vaillant ecotech plus 831, about 10 years old. Atm I do not have any problems with pressure, its 1.3 when cold, 1.8 when hot.

And its been serviced regularly, although I did have quite a few problems overall with it (twice diverter valve, pressure sensor, aav all been changed).

I also did more careful listening of where the sound occurs - its definitely top of the opposite side of where the bleeding valve is... I might try this - let it cool down, isolate valves and open up the top valves to let excess water and hopefully air out, then refill slightly and see how it goes...

 

[nwgs]

Turn one of the lock shields all the until it’s off. The open it up a bit until heating is coming through your radiator.

They don’t been to be fully open and that can cause the noise you’ve mentioned

 

[Someuser08]

This is what i've been doing all along, however at a point when its (almost) silent its also not very hot. Its in a bathroom which is used a lot, so I really need it to be at maximum heat there.

No other rads have this issue, apart from one in the kitchen, that has the same design, so that's why I'm thinking its something to do with that...

 

[Someuser08]

Another update. I did what I said I was going to do and bled an upstairs radiator from both sides after isolating it. Re-pressurised it slowly letting out all the air. Worked great. Not a sound the whole evening. Then decided to bleed another one the same way - I bit trickier as radiator was larger and a lot more water came out, but same result in the end - could not hear a thing.

Went to bed, didn't hear anything overnight, came to listen to them in the morning - a little faint sound did appear, but I thought I probably didnt get 100% of air out when re-pressurising, so kind of expected and can only be heard when close to the radiator anyway.

In the evening everything came back though - may be not as bad as it was, but pretty close. The only thing that happened during the day is the heating was off, so the radiators cooled down. It must have allowed dispersed air to concentrate again in one place. Really bad design of these...

Short of replacing the radiator I'm not sure what else to try...