I have a Vaillant Ecotec-plus boiler in a system with a header tank. When it got cold recently I turned up the heating level, but it started making regular kettling and then banging noises. After the banging the heating cycle stops for a few minutes and later restarts. I tried reducing the heat input (was 20 kW originally) down to 15 kW and that helped for a time but it did not heat the radiators quite enough. I assumed that sludge or scale might be reducing the flow of water to the boiler. The pump and diverter value are only about 3 years old and I have the pump on its highest setting, but the boiler is 10 years old, and the pipework and radiators are maybe 30 years old, so sludge build up is entirely possible. I last cleaned with F3 it a few years ago when replacing the pump and diverter value and of course refilled with Screwfix own-brand protector fluid.
So: earlier this week, to try to solve the banging, I drained the system, removed a good bit of brown water from the header tank and scraped out a deposit of sludge from the bottom of the tank, then refilled with fresh water and Fernox F3 cleaner. That seems to have made the problem worse - the knocking now happens at a much lower temperature so that to avoid banging the radiators are barely warm. I've bled all the radiators, all of them heat up a bit if they are all on at once, and if put on one at a time each one heats up quite well, so don't think there's any trapped air or any completely blocked pipes, but there could well be sludge in the system somewhere.
Any suggestions? From reading posts on this forum and elsewhere the following seem possible, but I've no idea which might work:
1. Draining and refillling with Fernox F1 protector and maybe a noise-reducing chemical like Sentinel X200
2. Getting a heating specialist to do a MagnaCleanse flush and fit a MagnaClean filter. But these only appear to remove magnetic sludge, and I don't know if all of it is.
3. Getting a professional to do a power flush with suitable cleaning chemicals to try to remove scale and sludge from the boiler and the rest of the system.
So: earlier this week, to try to solve the banging, I drained the system, removed a good bit of brown water from the header tank and scraped out a deposit of sludge from the bottom of the tank, then refilled with fresh water and Fernox F3 cleaner. That seems to have made the problem worse - the knocking now happens at a much lower temperature so that to avoid banging the radiators are barely warm. I've bled all the radiators, all of them heat up a bit if they are all on at once, and if put on one at a time each one heats up quite well, so don't think there's any trapped air or any completely blocked pipes, but there could well be sludge in the system somewhere.
Any suggestions? From reading posts on this forum and elsewhere the following seem possible, but I've no idea which might work:
1. Draining and refillling with Fernox F1 protector and maybe a noise-reducing chemical like Sentinel X200
2. Getting a heating specialist to do a MagnaCleanse flush and fit a MagnaClean filter. But these only appear to remove magnetic sludge, and I don't know if all of it is.
3. Getting a professional to do a power flush with suitable cleaning chemicals to try to remove scale and sludge from the boiler and the rest of the system.
