Plumbers - draining central heating system

BennyC

BennyC

BennyC

Soldato
Joined
25 Sep 2006
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Hi,

I think we have a few plumbers here and I'd really appreciate it if someone could help.

I currently have a tiler in doing the floor downstairs and also half height in the WC, as well as fitting a towel radiator. He's Italian and speaks broken English but is doing a very good job. The basin is out and the pipes are capped (no shut off valves) and the bog is also out.

Tomorrow he'll be tiling the walls of the WC and fitting the towel radiator. He asked me this morning about draining the central heating system. I wasn't quite sure if he was asking me how to or perhaps more likely where from. It's a new build (I think it's a closed system? I have a filling loop to repressurise) and I'm fairly certain I've seen one of the house builder's plumbers draining it down from the top of the boiler when a leaky locksheild needed replacing but I might be mistaken.

However having read a few websites it seems the process is to shut off the boiler (on a fused spur) and then find the radiator with a drain valve and let all the water out. Then when you've done whatever it was you planned on doing, refill the system via the filling loop, switch the boiler back on and check each radiator to bleed air initially (starting downstairs) and also again when warm, and then top the system up again to account for any lost pressure from bleeding.

Does this sound right? It may be he just wanted me to point out where the drain valve was but always handy to know.

Thanks,

Ben
 
A lot of new builds have radiator valves that can be closed down and the radiator isolated too so no draining down is required (unless you're cutting in to the pipes, doubtful though when you're tiling a room)

Otherwise you'll need to find the drain **** and run some hose out of the door (process is to close the flow and return on the boiler and turn off the electrics to the boiler, close all the rads down so you don't have to refill them, plug in hose to drain ****, and open valve)
 
Shouldn't be any need to drain the system, just shut of the valves both sides, disconnect the rad and drain the water from that rad into a bucket.

Draining the whole lot would be more hassle than you need for taking one radiator off.
 
Ronty said:
Shouldn't be any need to drain the system, just shut of the valves both sides, disconnect the rad and drain the water from that rad into a bucket.

Draining the whole lot would be more hassle than you need for taking one radiator off.
Click to expand...

Thanks, would that not require an additional shut off valve in addition to the existing radiator valves? as the radiator (including valves) is being changed.
 
Have you got an expansion tank in the loft? I see its a new build so unlikely but depends how new.

If so you can bung the feed and expansion pipes to airlock it and save the need for draining.

Otherwise drain the lot and whip the valve off, and don't forget to put some inhibitor back in once the job is done.
 
^^^

What he said.

There should be a drain valve on the lowest part of the system. If not, you can remove a downstairs rad and drain from there. Then fit a drain valve while the system is empty if you require.

Adding inhibitor will be easiest to do via the new towel radiator before you refill the system.
 
Bigpops said:
inhibitor
Click to expand...

I've just been told about this. I'll ask the tiler tomorrow if he intends to add any. I expect I'll be changing the radiator in my en suite in October this year, is it imperative it's added now rather than later?

Edit: Could I chuck some in via the filling loop?
 
Last edited:
I'd nip to B&Q or similar and pick up a litre. As mentioned, Sentinel X100 is good stuff, but it's £7 cheaper than B&Q (£11.99) if there's a screwfix near you. You'll want about 1 litre for up to 10 radiators.

Once all the plumbing is done, but before the system is refilled, simply remove the blank from the top of the towel radiator, and pour it in using a funnel. Once it's in there, replace the blank (it should have an o-ring to seal, so no need for ptfe or compound) and proceed to fill the system with the loop. There's a video on YouTube by ultimatehandyman: http://www.youtube.com/watch?v=BI3S8B7f_vY

When you change the other radiator, you'll need to add some more if you're draining it down again. Again it will be easiest via the towel rad while the system is empty.
 
BennyC said:
However having read a few websites it seems the process is to shut off the boiler (on a fused spur) and then find the radiator with a drain valve and let all the water out. Then when you've done whatever it was you planned on doing, refill the system via the filling loop, switch the boiler back on and check each radiator to bleed air initially (starting downstairs) and also again when warm, and then top the system up again to account for any lost pressure from bleeding.
Ben
Click to expand...

Yes basically. Don't forget to do the valve up when you refill.

I'm a bit confused if he is replacing a rad for a heated towel rail installing a towel rail. Though this doesn't really matter there are just ways around not draining the whole system down if just replacing.

The easiest way to add your x100 is in your towel rail.

When it is fitted isolate the valves so it doesn't fill with water. Remove the cap on the top, get a funnel and pour in the x100. Put the cap back on, open the valves and bleed the air out.

Edit: Beaten :o
 
Bigpops said:
I'd nip to B&Q or similar and pick up a litre. As mentioned, Sentinel X100 is good stuff, but it's £7 cheaper than B&Q (£11.99) if there's a screwfix near you. You'll want about 1 litre for up to 10 radiators.

Once all the plumbing is done, but before the system is refilled, simply remove the blank from the top of the towel radiator, and pour it in using a funnel. Once it's in there, replace the blank (it should have an o-ring to seal, so no need for ptfe or compound) and proceed to fill the system with the loop. There's a video on YouTube by ultimatehandyman: http://www.youtube.com/watch?v=BI3S8B7f_vY

When you change the other radiator, you'll need to add some more if you're draining it down again. Again it will be easiest via the towel rad while the system is empty.
Click to expand...

Marshstyles said:
Yes basically. Don't forget to do the valve up when you refill.

I'm a bit confused if he is replacing a rad for a heated towel rail installing a towel rail. Though this doesn't really matter there are just ways around not draining the whole system down if just replacing.

The easiest way to add your x100 is in your towel rail.

When it is fitted isolate the valves so it doesn't fill with water. Remove the cap on the top, get a funnel and pour in the x100. Put the cap back on, open the valves and bleed the air out.

Edit: Beaten :o
Click to expand...

Cheers guys, I forgot to mention it this morning before I left so we'll see if my text was clear enough. He's replacing a radiator for a heated towel rail in addition to tiling. He's doing a good job but it'd be more reassuring if his level of English was better.

If he doesn't add some in I guess I could always drain the system myself, chuck some in and then refill this weekend.
 
you don't have to drain the system, we had a radiator moved on saturday, it was capped off last month when we had work done.

We had to turn off the central heating the night before when we went to bed and they then froze the pipes leading into there the radiator, it worked really well. The plug lasts a couple of hours, easily enough time to fit the radiator.
 
nIckEl101 said:
you don't have to drain the system, we had a radiator moved on saturday, it was capped off last month when we had work done.

We had to turn off the central heating the night before when we went to bed and they then froze the pipes leading into there the radiator, it worked really well. The plug lasts a couple of hours, easily enough time to fit the radiator.
Click to expand...

Whilst this would be preferable his first trade is tiling with sufficient knowledge of plumbing to allow him to carry out his work. I don't think he has the necessary equipment to freeze the pipes unfortunately.

Hedge said:
Regarding inhibitor.. if the Towel rail has a vent at the top, you can remove the whole vent nut (its about an inch in diameter) and pour the inhibitor into the towel rail before sealing it back off and filling it.

(this is the bit i mean http://compare.ebay.co.uk/like/2008...ixedPriceItemTypes&var=sbar&adtype=pla&crdt=0)
Click to expand...

Yeah, I had a look at it all last night though I expect it will all have been installed & filled by the time I get home this evening. If it hasn't I'll grab some and have him chuck it in, if not I'll have to get it in via the filling loop.
 
You can get it in through the vent or plug on any rad, with a funnel and piece of rubber hose, just pour slowly! The next easiest way after the towel rail.
 
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