Hi,

I want to move a hot water radiator. I have a “conventional” DHW/
CH system with floor mounted boiler, expansion / header tank, two
pumps and hot water cylinder.

I have read up on the method to drain the system and it seem
straightforward. I just want to check if there are any gotchas or
things I might have misunderstood.

1) Switch off the CH by switching timer control to off and setting all
thermostats to lowest setting

2) Stop water supply into the header / expansion tank by tying off the
ball cock with piece of wood and string

3) Fit a hose between the system drain tap and the drain gulley. Open
the drain tap. Now this I'm a bit concerned about. Outside the front
door, below the step is a drain tap. Now I am guessing this is the CH
Drain as it is pretty much at the lowest point. in the whole system.
Could it be something else? Is there any way I can check?

4) As the system drains work down from the top of the house opening
the radiator bleed valves letting air in but closing the valve for a
minute if water comes out.

5) Work down through the house opening each radiator bleed valve.

6) Wait until no more water comes out of the drain tap.

7) Put lots of old material under the CH pipe to be cut. Cut the pipe
with one of those circular pipe cutters – the one that fits the pipe
not a “universal” one with a screw adjustment. The reason for the
“dedicated” cutter is the cut will be clean and at right angles to the
pipe. Some dirty water will come out of the pipe to be captured by the
old material. Cut the other pipe in the same way.

8) Fit the new pipe. The old pipe is copper and I'm thinking of
fitting some kind of “flexible pipe” with those “screw in” connectors
rather than using compression joints and more copper. The reason for
doing that is the flexible pipe will be easier to route and I need to
put in less joints (I don't have a copper pipe bender). Anyone have
an opinion on mixing copper and the flexible pipe? The new radiator
position will be quite close to the old but copper pipe would require
a few bends and joints that I want to avoid.

9) Connect up the rad wrapping all the threads using PTFE (?) tape.

10) Close the system drain tap and the rad bleed valves. Can/ should I
put some chemical in the header tank to “flush” the system? Then fill,
empty and refill? My worry is the descaler will be corrosive and lots
of little pin holes in joints will open up.

11) Whether I flush / descale or not, do I just put inhibitor in the
header ./ expansion tank before I fill the system for the final time?

12) As the system fills I open and close the rad bleed valves from the
bottom rad to the top until the rads are filled.

13) Check the new joints for water tightness.

14) Switch the system back on and check rads become hot.

15) Over the next few days bleed the rads again to release any
dissolved air that has come out after system has filled?

Have I missed any steps or things I need to check?

Thanks,


Clive