New rads fitted 4 weeks later one needing bled

[Robert Anderson]

morning guys just looking for some advice I think the answer is hopefully straight forward however just double checking got 3 new rads fitted a just over a month ago however one had a small leak which got sorted a 3-4 weeks ago last night I noticed one of upstairs rads had a slight cold patch not stone cold anyway when heating went off I bled it and it had a decent amount of air about 5-6 second of ffffffsssssing lol and the other 2 upstairs had a tiny bit over alldropping about 0.2-3bar am I correct I’m assuming this will be just air that’s settled at the highest point from refilling after the fitting and then the repair?

 

[Harvest Fields]

It should be yes. Did you make sure that you topped the pressure back up?

 

[Robert Anderson]

Yeh just did that this morning as waited to the system was fully cold n topped it back up to 1.5 bar that’s what it was prior to bleeding I just got a bit worried as I googled it n you start getting all this stuff about corrosion gasses building up etc as opposed to just air gathered due to refilling and started to worry it was something like that lol even tho the old radiators didn’t need bled at all and were about 25 years old, I thought it was just the air bubbles collecting in one area but just wanted to get a expert opinion it wasn’t cold as such just a patch on top left of rad was cooler but still pretty warm the rest of the rad was roasting. heating on just now after topping up

 

[Robert Anderson]

Also I know us non experts shouldn’t google these things lol bit like googling sore foot and then you have a terminal illness!! Thanks for the reply btw

 

[Scott_D]

Its normal for some air to work it's way to the top of the rads after a drain and refill

 

[fixitflav]

morning guys just looking for some advice I think the answer is hopefully straight forward however just double checking got 3 new rads fitted a just over a month ago however one had a small leak which got sorted a 3-4 weeks ago last night I noticed one of upstairs rads had a slight cold patch not stone cold anyway when heating went off I bled it and it had a decent amount of air about 5-6 second of ffffffsssssing lol and the other 2 upstairs had a tiny bit over alldropping about 0.2-3bar am I correct I’m assuming this will be just air that’s settled at the highest point from refilling after the fitting and then the repair?

Was inhibitor topped up when the rads were added? If not you should add some. Next time you bleed, check to see if the gas coming out will burn. If it does it's the result of corrosion and needs more inhibitor. Also you could take a sample of the water, add some bright wire nails. If they go rusty after a few days more inhibitor needed.

 

[Robert Anderson]

Its normal for some air to work it's way to the top of the rads after a drain and refill

Would it take a few weeks for that to work it’s way to the top also I’m assuming if the old rads never needed bled then corosdion gasses isn’t the problem

 

[fixitflav]

Would it take a few weeks for that to work it’s way to the top also I’m assuming if the old rads never needed bled then corrosion gasses isn’t the problem

You probably lost some system water when the new rads were fitted, and more fresh water will have gone in. So no corrosion gases before doesn't mean there isn't now.

 

[Chuck]

Next time you bleed, check to see if the gas coming out will burn.

I think this advice is dangerous. The information is of little value and there is a significant risk burning yourself and/or causing a fire. I've seen several cases where the person trying it didn't realise that hydrogen flames are (nearly) invisible and burned themselves quite badly.

If it does it's the result of corrosion and needs more inhibitor.

Not necessarily. It is normal for new radiators and pipework to evolve hydrogen for weeks, if not months, after installation while the passivating layer forms. Inhibitor doesn't stop this process, it just happens a bit slower (completes in months rather than weeks).

Also you could take a sample of the water, add some bright wire nails. If they go rusty after a few days more inhibitor needed.

This test needs two separate samples of water in sealed containers. One from the heating system and one from the kitchen tap to act as a control.

 

[Robert Anderson]

Ok thanks everyone seems a bit more complex than I had hoped I was hoping it may just be air from refil??

 

[Robert Anderson]

Also if it was gasses how long would it take them to build up again so how long roughly would the rad need bled again you talking weeks or months I’m not sure I want to continually spend the winter touching radiators lol

 

[Chuck]

Ok thanks everyone seems a bit more complex than I had hoped I was hoping it may just be air from refil??

It probably is just residual air. It could also be hydrogen from the new radiators/pipework forming a 'passivating layer'. As long as you are sure some inhibitor was added when the system was refilled you shouldn't worry at this point. Just touch the radiator where the air/hydrogen is collecting once a week and bleed it if it's cold along the top. It will probably slow down after a week and have stopped completely after six months.

5 seconds of ffffffsssssing through pinhole bleed-point is a tiny amount of gas. Nothing to worry about.

 

[Robert Anderson]

Perfect thanks it’s just a hassle I don’t really need as most folk don’t lol and I get a bit ocd with this type of thing so I appreciate everyone’s help and reassurance my mates/neighbour is a heating engineer has been for a while he fitted the rads n said last night it would just be settlement air as we had to refil couple of times to get the repair done which was a olive at a jaunty angle lol anyway just thought I would ask the forum too and as always very helpful cheers guys have a great day

 

[Riley]

Next time you bleed, check to see if the gas coming out will burn.

Really wouldn’t suggest trying this as it’s dangerous

 

[Robert Anderson]

Yeh I’m not sure I want to start fires from gasses in my house to be honest unless it’s my hob

 

[fixitflav]

This test needs two separate samples of water in sealed containers. One from the heating system and one from the kitchen tap to act as a control.

What does the control prove? If the rad water shows no rust on the test, it's OK, if it shows rust, need to add inhibitor. Whatever the tap water test does.

 

[fixitflav]

Yeh I’m not sure I want to start fires from gasses in my house to be honest unless it’s my hob

Please yourself, but it's not exactly a Wehrmacht WW2 flamethrower! I've done it a few times. It's only a flame about 20mm long. You could let it burn until water starts coming out, when it will go out, or put your thumb over it to put it out. Obviously you'll make sure there are no curtains etc hanging near, or you might set them alight with your match, irrespective of any burning gas!

 

[Robert Anderson]

Ok cheers for all your help

 

[Chuck]

What does the control prove? If the rad water shows no rust on the test, it's OK, if it shows rust, need to add inhibitor. Whatever the tap water test does.

It's to show that the nail has been in the water long enough for a noticeable amount of corrosion to occur in untreated water.

Strictly speaking, one should drive the nail through a couple of cm of copper pipe and use that that as the test sample.

 

[fixitflav]

It's to show that the nail has been in the water long enough for a noticeable amount of corrosion to occur in untreated water.

Strictly speaking, one should drive the nail through a couple of cm of copper pipe and use that that as the test sample.

OK fair enough, knowing how long the tap water sample takes to go rusty gives useful information. If the rad water test is OK at that point I would put it to one side and check it every week or so for several weeks, to make sure.