chronic air in radiators and concurrent boiler pressure rise - combi

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WB Combi boiler about 5 years old.
All new rads installed as part of rennovation installed (4 downstairs, 4 upstairs, - all modern designer ones, 3 of which are the tall column rads)
1960s 3 bed house with copper piping

Install finished about 3 months ago, all was working ok, no issues and was using CH and HW without issue.
About a month ago plumber came back to finish off and put inhibitor in system.

Fast forward to a few weeks ago and noticed the pressure relief valve was leaking water, (I may have had the CH on a few times for 30 minutes in the prior 2 weeks).
Pressure was 3 Bar
Bleed all rads and pressure dropped to 1.5 bar (lots of air from all rads, downstairs and up, most from the tall one upstairs)
One of the rads bled out black water slightly sludgy, others were clear.

Tried CH, 3 downstaris and 2 upstairs rads were very noisy (like awaterfall), also they were not heating up at all on one side - seemed to be the lock shield side)
Tried opening/closing lock shields - no difference

Currently;
boiler pressure slowly builds over 4-5 days and when I re bleed rads it drops again.
This happens even though I am not using CH - (i am using boiler by virtue of hot water)
rads still noisy and not heating up



I cant see any signs on any leaks (gutted if it is just finshed all florring and decoration etc)
Could the inhibitor have rleased some of the latent corrison / sludge (it could be a coincidence that problems reared after the inhibitor was put in)

Any other ideas appreciated - waiting for plumber to come back but hes avoiding me for now

Im a diy numpty, just been gogling until now.
 
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First thing to check- do you have a filling loop (where you top up boiler pressure)- if yes, turn off both valves (one at each end of the loop) and disconnect one end of the loop. It's not unknown for those valves to fail open (plastic handle turns but doesn't operate valve) so turn mains cold water off at the stoptap before doing this.
After that you may be into leaking heat exchanger so try easy fix first.

EDIT Added inhibitor did he- does the system have a Magnaclean or similar installed? Check cover is tight and valves are ON.
 
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Thanks for reply, not at home at moment but it does have a filling loop. Just googled magnaclean and yes thats whats attached to the boiler, so thanks and will check that as well.
Can I clarify/ask to see if that changes anything;

So after I have fully bled all the radiators, the boiler pressure goes back down to its baseline of 1.5bar after every bleed over the past few weeks.
So its baseline immediately after being bled is not increasing at all (1.5 bar) - does this mean it cant be water getting in as I would expect this baseline to rise over the past few weeks?

cheers.
 
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If you bleed the system, don't fire it up and the pressure stays constant for a day or more then it's not the filling loop. Don't expect to see instant anything- if the loop is passing it may only be overnight that mains water pressure is higher than your 1.5 bar. Pressure increasing fairly rapidly (almost as soon as the boiler starts heating the rads) would point towards expansion vessel being duff or needing repressurising (sometimes doable by end user but not always, check your boiler instructions)
 
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Do you know what inhibitor they used?

Sounds very much like system corrosion causing gassing in the rads, which will result in pressure build up if the gas is not released.

If you bleed gas from a rad, if you are careful, you can hold a test tube/similarly shaped strong container upside down above the bleed point as your venting. Then quickly take a lighter, turn the tube the normal way up and hold the lighter near the top. If you get a pop of a flame coming out the tube, you have confirmed that it is corrosion.

Reason being, "air" in rads, would do nothing. "Hydrogen" in rads would pop/burn when lit. Hydrogen is the by-product of system corrosion breaking down the water into Hydrogen and oxygen.

Unfortunately most "designer" rads are $hite. They might look nice, but great care needs taking in sizing, fitting and flushing of them for them to match decent normal panel convector radiators functionality.

Its very important they are first flushed out with cleaning chemicals, thoroughly. Flushed through then with as much water as it takes to remove all grease/oil/sediment/swarf that they usualy come with. Then a proper inhibitor added. Not any of the cheap trade $hite, Fernox or Adey is the only two I'd ever put near my system.
 
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Do you know what inhibitor they used?

Sounds very much like system corrosion causing gassing in the rads, which will result in pressure build up if the gas is not released.

If you bleed gas from a rad, if you are careful, you can hold a test tube/similarly shaped strong container upside down above the bleed point as your venting. Then quickly take a lighter, turn the tube the normal way up and hold the lighter near the top. If you get a pop of a flame coming out the tube, you have confirmed that it is corrosion.

Reason being, "air" in rads, would do nothing. "Hydrogen" in rads would pop/burn when lit. Hydrogen is the by-product of system corrosion breaking down the water into Hydrogen and oxygen.

Unfortunately most "designer" rads are $hite. They might look nice, but great care needs taking in sizing, fitting and flushing of them for them to match decent normal panel convector radiators functionality.

Its very important they are first flushed out with cleaning chemicals, thoroughly. Flushed through then with as much water as it takes to remove all grease/oil/sediment/swarf that they usualy come with. Then a proper inhibitor added. Not any of the cheap trade $hite, Fernox or Adey is the only two I'd ever put near my system.
Thanks very much!!, just did this and 100% popped, wtf. (I tried 2 rads and no pop but was using a wide tumbler, then found a slimmer necked tumbler more like a test tube like you instructed and it definitely 100% popped - just in case anyone else is reading)
Not sure what inhibitor was used, unfortunately. they are due back next week.

Hope you don't mind a few questions if you have time please

Are we talking about a power-flush (which I belive is north of £400) or is the flush you mentioned not the same. Will this likely cure it (Im not looking at changing pipes am I ?).

Not sure how to approach the plumber, should they be looking at resolving this without charge (they changed all the rads, including some minor pipe re-routing near the rads to accommodate the new sizes). I choose the rads myself (they didn't recommend)

I want to be fair to both sides, its at 1960/70 house and ive been in for 2 years, the work was really neat and tidy and at a fair price.
There was defo no problems before the plumbing work and rads were installed..

is it likely then new designer rads that would have caused this on their own, or does it suggest there was already latent corrosion ?

can I use the boiler with this issue (I can go elsewhere for showers, just for washing machine etc.) or will it fubar that (as I say they are back next week)



any thoughts welcome.
 
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Wonder what metal your designer rads are made of? If you're really unlucky you are getting galvanic corrosion (the inhibitor used has increased the electrical conductivity of the water thus enabling the process). Not sure if heating systems ever include a sacrificial anode (Google it if you're interested), the whole different metals bit is one big reason I've always avoided designer rads, towel rails etc.

Find out what inhibitor matey put in, it'll go on my Avoid list. System needs completely flushing through with mains water to start with- not necessarily a power flush, copious amounts of cold tap water to start with.
 
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@oldbutnotdead - could do with some advice please, you couldnt make this up.

The plumber came back about 10 days ago and said he did'nt use any cleaner, so after discussion (and me speaking with fernox tech - who were helpful) the system was drained down and fernox f3 cleaner put in, the system responded seemingly well and rads started heating up and making less noise. (also when drained he noticed the magnetic filter was well sludged up)
He was coming back tomorrow to drain/refill/drain/refill and then put inhibitor in.

I ran the heating system today just to circulate the cleaner one last time but then one of the rads sprang a leak at the bottom (I had turned the water temp on the boiler a bit) one of the vertical riser pipe weld joints, it looks like a pinhole and the paint had bubbled off (Ill try and get a photo)

It was leaking in a stream rather than dripping, only luck that I saw it!, its isolated now.

So it seems the corrosion has done this (in my mind too much coincidence to be a fault)

Im gutted as Im thinking the whole system is compromised and the damage to all the other rads is now done (but cant see it)

Im thinking of draining the system, getting inhibitor in it (or just leave it drained for the moment? as i dont need it) then getting a powerflush?

been reading about a magan clean as well.

There must some powerful corrosion to pinhole the rad in about 9 months (though I suppose 9 months is a wedge of time)#

Any words of advice appreciated.
 
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If the system is highly alkaline then it will corrode anything that's aluminium creating hydrogen. There are other causes but all are due to corrosion of one kind or another. The solution is the same though, cleaned, flushed, neutralised and then filled and inhibited. Also are the system pipes copper or pastic? If copper is it all cross bonded?

If cleaner is used, once flushed he needs to test the system to ensure that the system PH is back down to as close to neutral as possible, that's easy with the use of litmus paper. It's not a quick process and your chap needs to work through it properly.

Depending on where the leak is will determine whether the rad leak was caused by corrosion or not. If it is actually pinholed and the rad is aluminium then yes, 9 months is more than enough time to eat it's way through.
 
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Many thanks for that, during the course of things I got some litmus paper from amazon so will use that. (I tested myself at one point when all this started happening and it was neutral)
They are all copper pipes.
difficult to photograph but where the paint has bubbled off is where the leak came from. (vertical rad, bubbled off on rad itself at the weld junction of the riser pipe, a few inches from the trv)

The plumber doesn't do power flushing normally but has access to a fernox powerflush machine, I am better getting a specialist in?
When it's being done I guess its all flushed with cleaner first with the powerflush machine (goes in the cleaner?), then flushed through using the machine with plain water?

The supplier I spoke to will replace the rad, if they dont want it back will cut it open to see what its like inside (I know the guy who is local and never heard of them failing and sells them every other day )

My main concern is the fact that others may follow and Ill end up with a severe water damage after just finished doing everything.

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If it was neutral then it probably isn't aluminium corrosion, so it must be quite severe corrosion in the radiators, it needs to be pretty bad to create that amount of hydrogen.

Cleaner is usually added to the system and left for a week of two with the system being run an hoiur every day to circulate and let it work, then it's drain/flush/drain/flush till it all squeeky clean, then it's inhibit and monitor. if it starts to blackend again then keep repeating.

A power flush done properly will usually use stronger chemicals to clean and then powerflush, netralise and then inhibit, would normally take a full day or more, radiator numbers dependent.

My gripe would be with the installers, if the system had been properly installed it should never have got to this point IMO.

Just to clarify, you said 3 months in OP and then 9 months in last post, was the system run without inhibitor for 9 months?
 
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Thanks again, sorry for the confusion, yeah the rads were gradually installed bit by bit into the existing CH system from about 9 months ago and the last rad was installed about 3 months , (but I wasn't using the CH system until 3 months ago), the inhibitor was put in about a month ago (none was ever put in before then, I think they were waiting until last rad was installed, all rooms were being stripped back and re plastered etc). so it has been without inhibitor in until a month or so ago.

I'm really disappointed its got to this stage and worried about the damage done and the best way to make sure it doesn't get any worse so Im going to get the power flush done. Problem is im then in the hands of whoever does that to do it properly and dont live in a big city so not many to choose fromw
 
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Well, sounds like that's where your problem may have stemmed from, did they do any pipework replacement/soldering etc? Sounds like they didn't flush the system when the old rads were removed and then ran the new without a flush or inhibitor and the system's just gone corrosion mental. Seen it happen a few times, especially with non standard, designer rads and especially where the system wasn't properly inhibited from the start.

Your leak though may just be down to poor manufacturing, a lot of these bespoke rads unfortunately are imported & made from low grade metals and inferior construction/quality control.
 
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Yes, I would say a bit of pipework, but having said that it was for every rad, mainly to convert from floor to wall mounted (so the rad pipes cam out of the wall rather up through floor,, the rads were a different size) (they dint do any work on the core network of pipework, just the rad connection points) - Im guessing by you asking the question that work can significantly impact the system.

very much appreciate your time.
 
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If they soldered in new copper and didn't flush the system then that's a major factor. Flux is acidic and that coupled with no inhibitor will drastically accelarate system corrosion. If you also say you were getting black sludge out one radiator that's only been in for months then there's been something in there that's promoted corrosion, especially if you also have a mag filter.

It'll need a thorough clean and flush to get on top of it, then plenty of inhibitor, then regular checks for the first year to ensure it stays clean.
 

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