System Drain - Advice Please

[NorthernLad]

We live in a house that was extended in 1986, we arrived in 1991, and only now realise that there is no obvious way to drain the original downstairs radiators.

There are two drain cocks fitted on pipework drops that drain the upstairs/extension end of the house only. I suspect the lady of the house at that time had the missing drain point covered up somehow in her alterations.

So, yesterday I had added X400 and drained what turns out to be only about half the system.
I refilled and I am now left with about half strength X400 that needs to be drained.

I could drain again using existing drain cocks and refill leaving about quarter strength X400, but will still be unable to drain the whole system without an additional drain cock. Draining three double 6 foot rads and one single via the connections seems like it would take a while.

No exposed pipework available to fit a new drain cock apart from the short lengths up through wooden floor boards to the 1986 radiators.

Any suggestions welcome!

 

[Gasmk1]

Drain cock fitted to top of rad temporary to drain most, then change on of the lock shields to one with drain cock integral. you could do this by drawing one rad and freezing that side to fit the lockshield White Angled Manual Radiator Valve With Drain-Off 15mm x ½ - https://www.NoLinkingToThis/p/white-angled-manual-radiator-valve-with-drain-off-15mm-x-/70408?tc=JT7&ds_kid=92700058107811640&ds_rl=1249404&gclid=CjwKCAiA6seQBhAfEiwAvPqu16GJ4GOpy6lCr0PpXazRBCEZj7_1hfQJiu5-kGdj65TTZJ9X67kIzRoCZzYQAvD_BwE&gclsrc=aw.ds like this or similar

 

[NorthernLad]

Drain cock fitted to top of rad temporary to drain most, then change on of the lock shields to one with drain cock integral. you could do this by drawing one rad and freezing that side to fit the lockshield White Angled Manual Radiator Valve With Drain-Off 15mm x ½ - https://www.NoLinkingToThis/p/white-angled-manual-radiator-valve-with-drain-off-15mm-x-/70408?tc=JT7&ds_kid=92700058107811640&ds_rl=1249404&gclid=CjwKCAiA6seQBhAfEiwAvPqu16GJ4GOpy6lCr0PpXazRBCEZj7_1hfQJiu5-kGdj65TTZJ9X67kIzRoCZzYQAvD_BwE&gclsrc=aw.ds like this or similar

Thanks for that Gamsk 1 - Had one of those valves in the back of my mind but dont have the freezing kit.
May end up lifting floorboards in the loo, where the single radiator is, to cut pipework (which I hope I will be able to access) underneath to allow the drain to void before I can fit the valve.
Do you think I can I assume that I can leave the original tail fitted to the rad. and just use the new valve?

 

[Gasmk1]

Depends on valves now fitted

 

[NorthernLad]

Depends on valves now fitted

Thanks Gamsk 1 - Well, they 'look' the same - but as we all know they not be 'exactly' the same! Guess I just give it a go.