"Gas" in Radiators

[GraRob]

Have you tried bleeding the pump to see if you can get any air out and cure the 'whoosh' noise? There's a big screw in the centre of the pump which is the bleed screw for the pump.

Sounds like you have a leak somewhere in the system that is drawing in air. With no pumping over, inhibitor in the system and all radiators bled, you shouldn't be getting enough corrosion going on to fill the tops of your radiators.

Thanks, I captured some of the gas in an old beer bottle when bleeding this afternoon, and there was a definate "whoosh" (not a pop) when I stuck a long lighter into the neck. I'm going to do it again tomorrow just to be sure.

Ps; yes, I've bled the pump too. If the gas ignites or pops tomorrow, I'll drain the whole system, flush and stick in inhibitor and see how that goes.
Also, when the heating is on the radiators seem ok and dont need bled, theres always air or "gas' in the radiators when left overnight?

 

[ScottishGasMan]

Make sure you use good inhibitor not cheap trade stuff.

Stick to fernox or sentinel, ideally for gassing issues fernox MB1 used to be the best for it, but any good stuff should do the job once the systems been cleaned out.

Bear in mind after draining and flushing out a few times and refilling, it may take a few days depending on your system, to get all the air into the rads and vented out, so dont me too surprised if you do still have to bleed them over a short period after

 

[GraRob]

Make sure you use good inhibitor not cheap trade stuff.

Stick to fernox or sentinel, ideally for gassing issues fernox MB1 used to be the best for it, but any good stuff should do the job once the systems been cleaned out.

Bear in mind after draining and flushing out a few times and refilling, it may take a few days depending on your system, to get all the air into the rads and vented out, so dont me too surprised if you do still have to bleed them over a short period after

Good advice thanks SGM.

Well I did the bottle trick with the gas out the radiator, which I'd left over night & it did "pop", so i think it's quite conclusive that it's a build up of Hydrogen gas overnight due to excessive corrosion products in the water/radiators.

I've drained & flushed the system, and also removed & flushed a few radiators that are older. Suffice to say, the water coming out the drain was pretty bad. Last time the system water was changed was 2018. I think I'll need to do this annually.

System is now refilled with Fernox MB1, and the radiators seem to be much hotter than before. I'll monitor it and update once the system has settled down.

What is clear; if the system is sufficiently contaminated, it can produce enough hydrogen gas overnight to cause a radiator airlock.

 

[Madrab]

Buy some litmus paper .... do a test on the system water .... anything quite alkaline > 9 - 10 (dark green to blue) then it can cause corrosion with an aluminium HEX and create hydrogen in the system.

In effect it will eat the HEX from the inside.

 

[GraRob]

Buy some litmus paper .... do a test on the system water .... anything quite alkaline > 9 - 10 (dark green to blue) then it can cause corrosion with an aluminium HEX and create hydrogen in the system.

In effect it will eat the HEX from the inside.

Thanks, I'll run it for a couple of weeks then check water.

 

[Lower]

Good advice thanks SGM.

Well I did the bottle trick with the gas out the radiator, which I'd left over night & it did "pop", so i think it's quite conclusive that it's a build up of Hydrogen gas overnight due to excessive corrosion products in the water/radiators.

I've drained & flushed the system, and also removed & flushed a few radiators that are older. Suffice to say, the water coming out the drain was pretty bad. Last time the system water was changed was 2018. I think I'll need to do this annually.

System is now refilled with Fernox MB1, and the radiators seem to be much hotter than before. I'll monitor it and update once the system has settled down.

What is clear; if the system is sufficiently contaminated, it can produce enough hydrogen gas overnight to cause a radiator airlock.

Don’t drain it every year. Flush it to the point the water is coming out clear, put the inhibitor in to get the corrosion under control and then leave it.

if it’s not pumping over and you’ve got a magna clean, you shouldn’t drain it and refill it annually as you introduce fresh oxygenated water into the system every time which just causes more corrosion.

 

[GraRob]

Don’t drain it every year. Flush it to the point the water is coming out clear, put the inhibitor in to get the corrosion under control and then leave it.

if it’s not pumping over and you’ve got a magna clean, you shouldn’t drain it and refill it annually as you introduce fresh oxygenated water into the system every time which just causes more corrosion.

Thanks, and yes valid point, I did that 2 years ago, however the water in the whole system was pretty black this time.

 

[GraRob]

I thought I'd update this for completeness.

So system drained, flushed and refilled with MB1 inhibitor. Few days of settling in and bleeding etc. So over a week later and the system doesnt need bleed at all, and the offending towel radiators dont need bled either. I also think the automatic valves are working now too.

So it was in fact hydrogen gas being generated at an alarming rate - my fault for not draining and dosing the system.

Thanks to all on here for advice and help

 

[Mottie]

Buy some litmus paper .... do a test on the system water .... anything quite alkaline > 9 - 10 (dark green to blue) then it can cause corrosion with an aluminium HEX and create hydrogen in the system.

What should the litmus paper reading be for a boiler with an aluminium HEX?

 

[Madrab]

The litmus should be as close to neutral (7 - olive) as possible, CH water especially if it hasn't been flushed properly, will tend to be more alkaline. The more alkaline it is the more reactive it will be with aluminium to create hydrogen.