Hydrogen in Central Heating

[joshall]

Dear all,

I am constantly bleeding one radiator in a top bedroom, black sludge comes out and the gas is hydrogen, proven by a lighted match. I am also getting a small amount of gas in a second bedroom. The rads are cast iron and need replacing soon, but I also need to add inhibitor. I am not sure how the central heating system is laid out. My dilemma is, I am not sure what to do first. I am not sure if the corrosion is related to just the one rad or all over? I dont think I can afford to replace them all in one go.

Also how can I tell what radiotor is first to heat on the system. Tried testing with hand, they all seem to get hot quite quickly

 

[Slugbabydotcom]

The system needs flushing and inhibitor adding to protect the system.
Why do you need new rads? Are they leaking?
Who cares what rad gets hot first. Radiators are there to warm your house, not to race each other to see which one gets hot first

 

[doitall]

Hydrogen is a product of corrosion, either the system is full of sludge or the pipework is steel and past it's sell by date.

Powerflushing could solve one problem but destroy the pipework completely, expect a few leaks if it's really bad.

I would drain it all out and flush it with clean water a few times, to what if any difference it makes.

Need more info.

 

[joshall]

I am trying to figure out where the worst corrosion is, possibly pin it down to one or too rads. Although they are not leaking, we have been told they are cast iron and will need replacing soon. Also one of the TRV valves does not function. Could the corrosion be in the boiler too? is it usually localised or generally all over?

 

[ctp]

the corrosion will be on all ferrous/iron parts and poss heat exchanger in boiler , system needs cleaning.

 

[JohnD]

this is very common

if it is as old as it sounds, it will have a great deal of black sludge in it. the sludge is mostly black iron oxide caused by the corrosion of the iron or steel, and the hydrogen is released by the corrosion.

Start by draining it, this will remove some of the loose particles in suspension in the water. Fill and drain it a few times if you have time. When refilling, add one or two litres of Sentinel X400 which is a non-acidic sludge loosener that you leave in circulation for 4 weeks. You can get it at any DIY shed or plumbers merchant for £15. You need a 1% solution which is 1 litre in 20 gallons (100 litres) approx. It will help wash away the old sludge and will loosen hard deposits. You will know it is working when the fresh water goes jet black with loosened particles. It continues working for about 4 weeks after which it starts to lose its power.

After 4 weeks drain it out and rinse, it will have loosened a lot of old sludge, and you have to drain it all out before it has the chance to settle again. On final fill, add a litre or two of sentinel X100 (same places, same price) which is an inhibitor to prevent future corrosion.

For £100 you can buy a Magnaclean which is a device that traps black sludge out of the water and prevents new accumulations and blockages. however if your system is old and is made with iron pipes (not copper) then it is not an easy DIY job and i recommend you get an experienced old plumber to fit it for you.

BTW iron radiators can last 100 years depending on luck, water quality, and design of the system, so if they are not leaking yet you do not have to replace them. They are far thicker than modern pressed steel radiators so can tolerate worse corrosion. Look round the valves and vents for any signs of leaks or red rust.

 

[joshall]

If the rads do not need replacing.....no signs or rusts or leaks etc, you it be worth taking off the radiator that has the most gas in it and flushing it through with a hose pipe? would this be good enough to remove the sludge?

 

[JohnD]

that is a good method, but cast-iron rads are very heavy, and if they are on iron pipe are relatively difficult to work on, so personally I would not try it until necessary. On an old system, disturbing old joints makes them more likely to leak.

Pressed-steel rads and copper pipes are much easier to work on, and cheaper to repair or replace if they go wrong.

 

[doitall]

I am trying to figure out where the worst corrosion is, possibly pin it down to one or too rads. Although they are not leaking, we have been told they are cast iron and will need replacing soon. Also one of the TRV valves does not function. Could the corrosion be in the boiler too? is it usually localised or generally all over?

Need info about the system joshall, forget the rads they will last another 100 years.

What material and size are we talking for starters.

 

[Nige F]

Dear all,

I am also getting a small amount of gas in a second bedroom. The rads are cast iron and need replacing soon,

Who told you cast iron rads need replacing ...A scrappy or a Tinker

 

[joshall]

The pipes are copper. A magnet sticks to the radiator. I am beginning to wonder if they are pressed steel. They are shaped like the modern white single panel rads. How will I know the difference? WE have 6 rads in total. 3 on each floor. The largest being 2.25 m by 0.5m. System is open vented pumped and The boiler bangs

 

[JohnD]

They are shaped like the modern white single panel rads.

not cast iron then.

System is open vented pumped and The boiler bangs

Then start by giving it a good clean like I said. Bale out all the mud from the Feed and Expansion tank and sponge it clean first to avoid washing extra muck into the system. You can take steel rads off and hose them out in the garden prior to adding cleaning chemical. One litre will be enough. Replace any worn or leaky rad valves while you have it drained.

Look at the bottoms of the radiators for signs of pin-holes and leaks.

If you can do basic DIY plumbing you can fit a Magnaclean. It goes on a 22mm vertical return pipe to the boiler. On copper pipe it is fairly easy. I guarantee you will be amazed and delighted to see how much black sludge a Magnaclean traps. You empty it out periodically and it carries on working.

You can add a boiler-silencer chemical such as Sentinel X200 for limescale after you have dealt with most of the sediment and corrosion.