Are these outside heating drain off valves?

[waheed357]

Hi.

I am doing renovation on my ensuite and need to replace a radiator for a towel rail. It is also getting moved to a different wall. There isn't a drain off on any radiators and once i did some research, I found these drain offs outside (photo). I wanted to ask if these are definitely heating drain offs and also there are 2. Do I just use any one of them to drain the system or both. Its a 2 story house with loads of radiators so any advice on how to drain the system and also how to properly fill the system would be greatly appreciated. The ensuite is upstairs. I've watched a few tutorials but a bit confused on whether I need to bleed every single radiator on both levels while re pressurise the system and is it to be done slowly going back and forth to radiators to bleed them. Thanks.

 

[dilalio]

I'd be using them as drain offs.
One can never say definitely as I'm not there.
To change a high level rad you don't need to drain the whole system but if it's not been done for a while then it's good maintenance to do so.
There's 2 because one is on flow the other return so open them both.
Also open air vents on upstairs rads as it starts to drain - the will suck air in as system empties.
Then open vents on lower rads to completely empty it.
Get new washers for the drain cocks for when you refill.
Would also be worth running a cleaner round it for a few days.
Emptying it again and then refill with inhibitor.
Don't forget to close air vents.

 

[waheed357]

Thank you so much. Would the cleaner work even if the heating stays off or do I need to turn it for a bit for it to work? Not the weather to put the heating on at all.

Also, when I refill the system, do I just shut the vents on all radiators before doing it or do I need to bleed them as i refill the system. Thanks again

 

[dilalio]

Thank you so much. Would the cleaner work even if the heating stays off or do I need to turn it for a bit for it to work? Not the weather to put the heating on at all.

Also, when I refill the system, do I just shut the vents on all radiators before doing it or do I need to bleed them as i refill the system. Thanks again

Cleaner works via circulation so yes you need to put the heating on.
It is what it is.
Depending on the condition of the dumped system water, you could just use the filling loop to flush through each rad (I think you said it's a sealed system).

You'll need to bleed all rads when refilling... Lowest first then highest.