A little help with sludge busting please?

[Slippery]

Hi all,

We recently moved into an eight bed victorian B&B. Th previous owners had a very, very relaxed attitude to maintenance and improvement!
We have found two radiators that have leaked (perforated), suggesting inhibitor wasn't used for some period. On removing one on the ground floor, it was found to be very sludged up. There are two or three more radiators on the ground floor that are cool at the bottom so I'm proposing to remove them, flush them and refit.
There is a magnetic filter near the boiler that I want to clean out too.
I was hoping to avoid draining the system but thought adding some inhibitor to the tank would be a good idea.
So really, what's the correct sequence here, rads, then filter, then add inhibitor, then fill rads?
The system is fed by a plastic tank in the loft. I found this to be lukewarm last time I looked.

(PS, I've been a carpenter/builder for almost thirty years, but have very little experience in heating, so I have plenty of practical experience, just little knowledge)

 

[moonlight]

The little tank will be warm as the water from the heating will expand into it especially if you have some blocked pipework. I would suggest, try venting some radiators and see if the small tank refills, if not you have a bigger problem with sludge. If it fills make sure the radiators you are taking off the valves close on both ends. Close valves, open air vent if water eventually stops the valves are off and you can drain and remove the single radiator and clean and flush. Refit before going onto the next that way you have only two joints to check at anyone time. Repeat for any radiators you want to clean. Depending on which magnetic filter you have will determine how easy it is to clean. Isolate, check vent, no water open and clean. Don't add the inhibitor to the tank it will sit in the bottom and solidify (slime, yuk). You could add it to the filter if you have a magna clean unit. Right in the heart of the system.

 

[Slippery]

Thank you @moonlight!