blackrose Posted November 13, 2021 Report Share Posted November 13, 2021 (edited) 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 November 13, 2021 by blackrose Link to comment Share on other sites More sharing options...
Popular Post David Mack Posted November 13, 2021 Popular Post Report Share Posted November 13, 2021 (edited) I would be inclined to drain down the system, disconnect the pipe connections to each radiator, lift the radiator out onto the bank and stick the hosepipe in one end. That way you can be sure the radiator is clear of sludge. Other approaches could clean the pipework but leave a fair bit of sludge in the radiators. And put some proper corrosion inhibitor in on refilling to prevent further sludging. Edited November 13, 2021 by David Mack 5 Link to comment Share on other sites More sharing options...
Onewheeler Posted November 13, 2021 Report Share Posted November 13, 2021 The sludge remover stuff is quite good but I suspect would need a pumped system with the pump running hard. Link to comment Share on other sites More sharing options...
GUMPY Posted November 13, 2021 Report Share Posted November 13, 2021 When we moved in here the rads were sludgey so I binned them all and replaced them, no more sludge 1 Link to comment Share on other sites More sharing options...
blackrose Posted November 13, 2021 Author Report Share Posted November 13, 2021 I'll try to pressure clean the whole system with a hosepipe. Mains water pressure at my moorings is pretty good. It's only a small system with 2 rads. I'll just have to take care not to flood the boat! Then I'll put sludge remover in the system for a few weeks. Link to comment Share on other sites More sharing options...
Ex Brummie Posted November 13, 2021 Report Share Posted November 13, 2021 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. Link to comment Share on other sites More sharing options...
Cheshire cat Posted November 13, 2021 Report Share Posted November 13, 2021 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. Link to comment Share on other sites More sharing options...
cuthound Posted November 16, 2021 Report Share Posted November 16, 2021 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. Link to comment Share on other sites More sharing options...
blackrose Posted December 27, 2021 Author Report Share Posted December 27, 2021 (edited) 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 December 27, 2021 by blackrose Link to comment Share on other sites More sharing options...
Ex Brummie Posted December 27, 2021 Report Share Posted December 27, 2021 (edited) 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 December 27, 2021 by Ex Brummie 2 Link to comment Share on other sites More sharing options...
George and Dragon Posted December 27, 2021 Report Share Posted December 27, 2021 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. Link to comment Share on other sites More sharing options...
Ex Brummie Posted December 27, 2021 Report Share Posted December 27, 2021 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. Link to comment Share on other sites More sharing options...
Cheshire cat Posted December 27, 2021 Report Share Posted December 27, 2021 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. Link to comment Share on other sites More sharing options...
Ronaldo47 Posted December 28, 2021 Report Share Posted December 28, 2021 (edited) 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 December 28, 2021 by Ronaldo47 typos Link to comment Share on other sites More sharing options...
blackrose Posted December 28, 2021 Author Report Share Posted December 28, 2021 (edited) 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 December 28, 2021 by blackrose Link to comment Share on other sites More sharing options...
blackrose Posted December 28, 2021 Author Report Share Posted December 28, 2021 8 hours ago, Ronaldo47 said: 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! Or using PTFE tape properly. Link to comment Share on other sites More sharing options...
GUMPY Posted December 28, 2021 Report Share Posted December 28, 2021 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 🤭 Link to comment Share on other sites More sharing options...
Ex Brummie Posted December 28, 2021 Report Share Posted December 28, 2021 57 minutes ago, blackrose said: I though an air lock would mean the rad was cold at the top not at the bottom? A partial air lock in the pipework can let a reduced amount of water through leading to the symptoms you have. Link to comment Share on other sites More sharing options...
Ronaldo47 Posted December 28, 2021 Report Share Posted December 28, 2021 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. Link to comment Share on other sites More sharing options...
blackrose Posted December 28, 2021 Author Report Share Posted December 28, 2021 (edited) 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 December 28, 2021 by blackrose 1 Link to comment Share on other sites More sharing options...
blackrose Posted December 28, 2021 Author Report Share Posted December 28, 2021 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. Link to comment Share on other sites More sharing options...
ditchcrawler Posted December 28, 2021 Report Share Posted December 28, 2021 11 hours ago, blackrose said: 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. Have you added new antifreeze? Link to comment Share on other sites More sharing options...
blackrose Posted May 29, 2022 Author Report Share Posted May 29, 2022 (edited) On 13/11/2021 at 11:45, Loddon said: When we moved in here the rads were sludgey so I binned them all and replaced them, no more sludge Well the odd thing is that the rad that's sludgey is brand new - replaced last year. Anyway, finally got around to taking it off today and the other odd thing is that the sludge was all at the top of the rad! I thought it would be at the bottom. The top port of the rad was totally blocked as well as the connection to the C/H system. I've unblocked the connection and flushed out the rad with a hose out and also unblocked the top port to the C/H system and sucked out both top and bottom port to the C/H system with a wetvac. I just hope the sludge isn't in the rest of the system too because that's impossible to flush out without dismantling the whole thing. I don't think it can be too bad because the rest of the system was getting hot. It almost seems like the sludge was in the new rad from the start? Edited May 29, 2022 by blackrose Link to comment Share on other sites More sharing options...
Ronaldo47 Posted May 29, 2022 Report Share Posted May 29, 2022 (edited) When I installed brand new gas-fired central heating in my first house to replace its storage radiators, the circulating water turned black within a few months. I was advised by a chemist friend to put some corrosion inhibitor in the system to prevent sludge generation. The house we are in now had no inhibitor fitted when we got it, and after removing and cleaning all the radiators, flushing the pipes, and dosing with inhibitor, it took around 20 years before I stopped having to remove the pump every year to wire-brush the black magnetic iron oxide that couldn't be removed by flushing, from the rotor. When the system was drained three years ago to fit radiators in our new extension, the 15-year-old circulating water (dosed with Fernox MB4 inhibitor) was still clear. The original radiators, installed more than 50 years ago, are still in use. In an unprotected system, electrolytic reaction between copper and iron, produces black magnetic ferrous oxide at the iron, and hydrogen gas at the copper. But the sludge normally collects at the bottom of the radiators in an unprotected system . Edited May 29, 2022 by Ronaldo47 Link to comment Share on other sites More sharing options...
blackrose Posted May 29, 2022 Author Report Share Posted May 29, 2022 I've had Ankorsol corrosion inhibitor in the system for a few years. Before that I was using Fernox. Link to comment Share on other sites More sharing options...
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