Draining system with rads closed

[jammmy]

Hi, I am looking to replace the bathroom radiator with a towel rail (I will only be doing the pipe work and capping it not installing the rail until I have tiled).
Anyway I only have to drain off the top half of the system and the tight arse in me doesn't want to waste the 2 lots of inhibitor (sentinel) i put in there about 6 months ago.
If I close all the upstairs rads off and drain the top half will this be alright when I refill the system in terms of there being enough inhibitor bearing in mind I used 2 doses before when I probably only needed one.
Hope that makes sense, than ks for any help.

 

[JohnD]

probably

but if like me you are very mean, drain it into buckets.

then you will see how much you have lost (also how dirty it is)

if you feel like it, you can tip it back in the F&E after (but I would put it through a cheap paper coffee filter and let it settle, unless it is already clear)

empty the F&E into another bucket before you start, and sponge out any mud.

if you use rubber bungs you will lose very little water and it will stop coming out of the drain when it has created a vacuum. In this case deal with one pipe at a time. If you have more than one pipe open you may lose the vacuum.

btw if you use service valves (ball-o-fix type) it will save you draining again when you are ready to fit the towel rail. Or if you already have the towel rail, you can fit its TRV and lockshield ready for later.

 

[shambolic]

And I thought us Scots were meant to be tight FFS!!!!!
Just drain the whole thing and do a hot and cold flush after the work and ad new inhibitor.
In fact put cleanser in the week before and go the whole way you tightwad!!!

 

[jammmy]

Thanks lads, I'm off to find my buckets.