Steel wool either in a pack of 3 by Rothenberger in a medium grade and a single large roll of Medium grade steel wool.

Draper 90003 15mm / 22mm Pipe Cleaner and Deburrer

So I put some cleaner in the system (I was intending to anyway after a few days of sorting the system). I did this from both 1st floor upwards (with discharge to 2nd floor) and from 2nd floor downwards (with discharge at 1st floor). I'm currently in the process of ramping up the thermastat slowly (over the next few days I'll get to max) so we'll see how we get on. High-performance and a long-lasting alternative to traditional sandpapers that are usually non-splintering and non-rusting. Some products may be delivered straight to your door from one of our suppliers and these products will be labelled within the product description.Initially the noises didn't subside but I knocked the thermastat back to min and ran it for about 8hrs. Rothenberger Rovlies come in a pack of 10, these cleaning pads are designed to be used for cleaning ends of copper pipe prior to soldering. After about 30secs a huge glug occured and black water came out I left it running for about 10mins to clear as much sludge as I could. I confirmed this by placing a magnet on a piece of copper pipe and getting a magnetic force (which indicated a ferrous material must be inside the copper). They are suitable for removing corrosion, oil and grease and can be used in both wet and dry conditions.

Silverline Pipe Cleaner Deburrer 15mm 22mm | Homebase

Thanks KIAB - I have recently installed a magnetic filter so I'm hoping this will pick up lots of the sludge. PS - the reason rads occassionally got lukewarm was because of natural convection within the system. These plastic pipes had also been laid to create a natural low spot (which I think is significant as it acts as a settling point for sludge when the water isn't circulating). A plumber's choice for a robust, waterproof material and essential for cleaning in wet and dry conditions. No3 medium grade steel wool is used for general purpose work, cleaning or copper pipe and fittings, paint removal and preparation of pipework.High-performance and a long lasting alternative to traditional sandpapers that are usually non-splintering and non-rusting. When I did this I could see that the 2nd floor system had been added at a later date from the rest of the house as the main pipe runs were all copper and the 2nd floor was all plastic. If incorrect pipe only suitable for hot and cold water, then they will block solid due to ingress of air through pipe walls. g. balancing the system, bleeding the system, trying to force flow to the cold rads by closing every warm rad, uprating the central heating pump, flushing the affected rads, checking the rad valves were functioning properly.