Bleeding Radiator, but it's not air!

[Hightower]

It's gas!

I've been getting a slow build up of air in one of my central heating radiators over the winter. It's been more annoying than troublesome. I was talking to someone earlier in the week about possible causes and where the air might be entering from. Somebody earwigging said it might be flammable gas produced by a build up of sludge in the system. So I thought I'd test this theory today. I lit my BBQ lighter and opened the bleed valve. To my surprise the gas escaping ignited and burnt off with a nearly invisible flame.

Anyone else experienced this?

[Erin]

Sounds like the by-product of electrolysis or corrosion of some sort producing weak hydrogen mix perhaps. Good dose of inhibitor might help.

[Hightower]

Originally Posted by Erin

Sounds like the by-product of electrolysis or corrosion of some sort producing weak hydrogen mix perhaps. Good dose of inhibitor might help.

That's the strange thing. I had the kitchen stripped out 3 years ago and had a bit of work done by installing a radiator in the kitchen and conservatory. Inhibitor was used when refilling.

[Andy B]

Originally Posted by Erin

Sounds like the by-product of electrolysis or corrosion of some sort producing weak hydrogen mix perhaps. Good dose of inhibitor might help.

i'd give the system a good flush first,
how olds your system?
if it's more than a couple of years then i'd recomend this stuff
Sentinel x400 Sludge Remover System Restorer.
if it's a newer system then use
Sentinel X300 System Cleaner.
hang on, give this a read this
http://www.buyaparcel.com/pageview.p...ckcode=7120725

[Andy B]

Originally Posted by Hightower

3 years ago and had a bit of work done by installing a radiator in the kitchen and conservatory.

and it would have been at that point that the sludge that was happily sat in your system was desturbed

[Hightower]

I'd have said that the majority of the radiators are as old as the house (1974). The boiler was replaced and relocated in 1995 and the tank and system was upgraded from a gravity fed to a fully pumped system at that time too.

I figured earlier today that the system would need cleaning. When flushing the system, do I have to remove all the radiators and force flush them with a hose? Or just empty the system, fill with a cleaning agent and then empty again.

[willk]

If your system is "open" (expansion tank in roofspace) then it will refill if leaking/weeping also diluting the inhibitor.

You shouldn't be getting air build up. I'd tie up the valve at the expansion tank and check for leakage over a few days.

EDIT: Cleaning rads is a barsteward of a job.

[Andy B]

Originally Posted by Hightower

When flushing the system, do I have to remove all the radiators and force flush them with a hose? Or just empty the system.

All you have to do is add the flushing agent to the existing water in the system,
then run the heating for a minimum of 2hrs but i'd leave it running for a couple of days.
The flushing agent breaks down the sludge so that it circulates around the system and is not in a sedimentary state!
After it has been in the system for a couple of days drain the system and refill with fresh water and inhibitor.
If the water was very black when you drained down then you could just fill the system with water only,
run for a few hours then drain down then refill with water and inhibitor.

if you have an open system with a tank then stop of the valve and drain down enough water to empty the tank,
add the flushing agent to the empty tank then unstop the valve to allow the tank/system to refill.
if you have a closed system,(no tank) then drain down the system a little then add the flushing agent to an upstairs rad.
then refill and vent rads

[Hightower]

It's an open system with a tank in the loft. I'll wait till the warmer months, when I'm not in need of the central heating before carrying out the flush.

But has anyone heard of combustible gasses building up in a heating system before? This was a new one to me

[willk]

Yes, often. Don't sweat it, it happens in people too