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Sludge in radiators


blackrose
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One of the radiators in the gravity/convection central heating system from my stove backboiler is getting hot at the top but not at the bottom which I think indicates sludge in the system?

 

It's odd as I replaced that radiator a couple of years ago after the old one sprung a leak.

 

I'm draining down the system now but what's the best way of flushing the system out? I could stick a hosepipe from outside into the car heater hose connected to the header tank at the top of the system and take the drain tap at the bottom of the system off completely and try to flush it out that way? I don't really want to start taking the rads off.

 

Should I use something like this?

 

https://www.screwfix.com/p/sentinel-x400-system-restorer-1ltr/89458?tc=VA5&ds_kid=92700055281954502&ds_rl=1249404&gclid=Cj0KCQiA4b2MBhD2ARIsAIrcB-S6KBrRPHnhvzMgmtyMcAPaiwybn1vIsU1zO6LEOcy7lUMP6ltSSbMaAiA6EALw_wcB&gclsrc=aw.ds

Edited by blackrose
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On a gravity system, it is not necessarily sludge in the rad, but could be an obstruction impeding flow. The hot still rises but not enough to warm the whole rad. For a 2 rad system, I would remove them to clean and then you can also clean out the pipework. Trying to flush the pipework with the rads in is not likely to be too successful.

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Not boaty but on my home system I installed a magnet https://www.amazon.co.uk/Magnaclean-189300-Magnetic-Filter-Black/dp/B003BNL8Z4/ref=asc_df_B003BNL8Z4/?tag=googshopuk-21&linkCode=df0&hvadid=235214917321&hvpos=&hvnetw=g&hvrand=2438677301247827733&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9046455&hvtargid=pla-368615768527&psc=1&th=1&psc=1

 

I thought it was snake oil when the boiler installer recommended it but It's amazing how much iron decay it hoovers up. No wonder the rads become compromised. 

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On 13/11/2021 at 20:10, Cheshire cat said:

Not boaty but on my home system I installed a magnet https://www.amazon.co.uk/Magnaclean-189300-Magnetic-Filter-Black/dp/B003BNL8Z4/ref=asc_df_B003BNL8Z4/?tag=googshopuk-21&linkCode=df0&hvadid=235214917321&hvpos=&hvnetw=g&hvrand=2438677301247827733&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9046455&hvtargid=pla-368615768527&psc=1&th=1&psc=1

 

I thought it was snake oil when the boiler installer recommended it but It's amazing how much iron decay it hoovers up. No wonder the rads become compromised. 

 

I came across Magnafilters during one of my last projects before I retired, where we utilised the waste heat from the exhaust of a hospitals gas turbine combined heat and power system to heat water which was circulated between 6 blocks of nearby council owned flats to provide domestic hot water a year round and preheat the central heating system in winter. The Magnafilters were used on the council flats side of the plate heat exchangers to remove the vast quantities of magnatite circulating in the council (lack of) maintained central heating systems.

 

I was so impressed that I fitted a domestic one to the central heating system of the house I had just moved into, which had old radiators but a brand new boiler.

 

For the first year I cleaned the filter monthly and removed a lot of magnetite but by the end of the year the water was (and has remained) clear. Best £100 I have ever spent on my central heating system.

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  • 1 month later...

I've had sludge remover in the system for the past couple of months which ideally is supposed to be used in conjunction with power-flushing, but the instructions say can be used without if you leave it in for several weeks. I haven't drained the system yet but the odd thing is the worst rad which is stone cold at the bottom is the new one I installed about 18 months ago to replace a leaking rad. I vaguely remember reading something about flushing out new CH rads before installing which I didn't do because I thought if it was that important the manufacturer should have done it! Is that why the new rad is bad?

 

I'm planning to drain the system this week as the weather is supposed to warm up a bit. I'll half refill and wetvac it out a couple of time to see if I can remove any sludge that way. There's also the option of attaching hoses at the top and bottom of the system to try to power-flush without taking the rads off. The last option is taking the rads off to clean them out but I wouldn't do that until summer.

 

On 13/11/2021 at 17:44, Ex Brummie said:

On a gravity system, it is not necessarily sludge in the rad, but could be an obstruction impeding flow. The hot still rises but not enough to warm the whole rad. For a 2 rad system, I would remove them to clean and then you can also clean out the pipework. Trying to flush the pipework with the rads in is not likely to be too successful.

 

What sort of obstruction would that be if not sludge?

Edited by blackrose
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57 minutes ago, blackrose said:

I've had sludge remover in the system for the past couple of months which ideally is supposed to be used in conjunction with power-flushing, but the instructions say can be used without if you leave it in for several weeks. I haven't drained the system yet but the odd thing is the worst rad which is stone cold at the bottom is the new one I installed about 18 months ago to replace a leaking rad. I vaguely remember reading something about flushing out new CH rads before installing which I didn't do because I thought if it was that important the manufacturer should have done it! Is that why the new rad is bad?

 

I'm planning to drain the system this week as the weather is supposed to warm up a bit. I'll half refill and wetvac it out a couple of time to see if I can remove any sludge that way. There's also the option of attaching hoses at the top and bottom of the system to try to power-flush without taking the rads off. The last option is taking the rads off to clean them out but I wouldn't do that until summer.

 

 

What sort of obstruction would that be if not sludge?

Stuck valve or disintegrating washer on seat. Could even be air lock on a gravity system.

Edited by Ex Brummie
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11 hours ago, blackrose said:

I vaguely remember reading something about flushing out new CH rads before installing which I didn't do because I thought if it was that important the manufacturer should have done it! Is that why the new rad is bad?

 

I've made similar mistakes in the past when I believed that manufacturers would be interested in repeat custom. They're not. They just want your money. With a few exceptions the trade knows what needs to be done and depending on the customer may take the requisite action. They too want your money but have to try to work out whether you're likely to be a repeat customer and whether you'll be calling them back within the warranty period.

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2 hours ago, George and Dragon said:

I've made similar mistakes in the past when I believed that manufacturers would be interested in repeat custom. They're not. They just want your money. With a few exceptions the trade knows what needs to be done and depending on the customer may take the requisite action. They too want your money but have to try to work out whether you're likely to be a repeat customer and whether you'll be calling them back within the warranty period.

I've never fitted a new rad that was blocked. Then again, I've attended to several that were blocked by self fitted belt and braces DIYers with excess/badly placed PTFE tape.

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   Then again, I've attended to several that were blocked by self fitted belt and braces DIYers with excess/badly placed PTFE tape

 

A good reason for using jointing paste!

 

Wheb we moved here over 40 years ago, the then-12 year old system had not been provided with any inhibitor. The circulating water was black ink and the radiators, although working, proved to contain a lot of sludge. They were all removed, thoroughly flushed with water, as were the pipes, before re-filling and adding  Fernox, which I had used in my previous house. I had never heard of dedicated magnetic filters then, but the circulating pump acted as one, requiring regular (initially at  approx 6 months) removal to clean the rotor and stator with steel wool to keep it working. I ended up fitting a plug and socket to the pump cable   to facilitate removal. It took more than 10 years before regular cleaning  was no longer necessary. The system had been installed by the old  North Thames Gas, whose installers must have been graduates of the  cowboy school of plumbing, but that's another story.

 

My suspicious mind wonders if 1970's  installers didn't bother fitting corrosion  inhibitor to ensure  regular repeat business in pump/radiator  replacement:  our pressed steel radiators must now be over 55 years old, and our present pump was fitted more than 15 years ago.  The previous one was only replaced at a similar age  due to failure of the  "O"ring seal of the shaft inspection cap that had allowed water into the electrics, causing a  short.  

Edited by Ronaldo47
typos
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22 hours ago, Ex Brummie said:

Stuck valve or disintegrating washer on seat. Could even be air lock on a gravity system.

 

I though an air lock would mean the rad was cold at the top not at the bottom?

 

10 hours ago, Ex Brummie said:

I've never fitted a new rad that was blocked. Then again, I've attended to several that were blocked by self fitted belt and braces DIYers with excess/badly placed PTFE tape.

 

The thing is it wasn't cold at the bottom last winter after I fitted it, It's only started behaving this way this winter. 

 

9 hours ago, Cheshire cat said:

Remove each radiator from the system, take it outside and pour water through it. When it runs clear take it back inside and reconnect it to the system.

 

As I said in my previous post, I will do that if the other options don't work. But I won't be removing rads in the middle of winter while the stove is required.

Edited by blackrose
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17 minutes ago, blackrose said:

 

As I said in my previous post, I will do that if the other options don't work. But I won't be removing rads in the middle of winter while the stove is required.

It's going to be above 15C for the next 4 days so perfect for heating work 🤭

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That was what we had when we had an extension built.  The new radiator wasn't putting out much heat until I turned off all the other radiators and set the pump to the highest setting. You could hear the gurgle as the air was flushed through the pipes  into the radiator, which was then fine after it had been bled. 

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2 hours ago, Loddon said:

It's going to be above 15C for the next 4 days so perfect for heating work 🤭

 

Above 15C at night? I doubt it. I'm working from tomorrow anyway.

 

2 hours ago, Ex Brummie said:

A partial air lock in the pipework can let a reduced amount of water through leading to the symptoms you have.

 

Ok, but I don't think it could be an airlock in my case as the system is self bleeding with the header tank at the highest point. There's nowhere for an airlock to form.

Edited by blackrose
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21 minutes ago, Ronaldo47 said:

That was what we had when we had an extension built.  The new radiator wasn't putting out much heat until I turned off all the other radiators and set the pump to the highest setting. You could hear the gurgle as the air was flushed through the pipes  into the radiator, which was then fine after it had been bled. 

 

System is self-bleeding, it's definitely not an airlock. I have a bleed valve on the top of the main run but it doesn't really do anything as the header tank is higher. The rad was bled when it was first installed but again not necessary as there was no air in the system because it had all self-bled.

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