Pipe freeze kit to add a drain off valve

VDFUser22

I have two broken valves on upstairs radiators which I want to replace as well as to refix a radiator to a wall. I plan to drain the system so while I'm at it I might as well drain the whole thing and change a valve downstairs for one with a drain off. I was thinking of using a freeze kit (Arctic Hayes from Screwfix) to freeze the downstairs pipe to add the drain off and then do a drain before replacing the upstairs valves.

And on refilling, does it sound right that my refill is just a pipe from the attic header tank (only a single tank up there not a dedicated F+E tank) that goes to a one way valve and then into the return pipes? There's a valve wheel too which is open. I've not seen anything similar on either YT videos (all UK videos though) or the boiler install manual.

Any thoughts on this?

Lenar3556

You could freeze it if there is enough space, to fit the jacket. Although most wouldn’t bother. It is usually reasonably easy to drain down the radiator and empty the system via either valve once you have the radiator removed. You can the fit on of those valves with the drain off you describe.

The arrangement you describe is what is called a semi sealed system. Quite common, although not great, as invariably the non return valve lets by and small quantities of central heating water makes its way into the tank. You could convert this to a sealed system, which would be a better job. The only caveat is that the central heating system will then run at a higher pressure than it did previously. Approx 2-3 bar vs perhaps 0.4 currently. In a new installation this is no issue, but in an older setup you could expose leaks in pipework.