How to drain radiator ?

[swayzak]

Hi

This is a really basic question.

There is a drainage tap on my downstairs radiator, which I wish to use in order to add some Sentinel X100 & X200 to the CH system.

It has a small square bolt protruding from the side (looks as though a key should fit it, but my radiator bleed key is just too small).

There is also a flat tab sticking up vertically (underlying the plastic cover).

How do I open this tap (I've never done it before) ?

thanks

 

[StephenW]

I assume you're talking about something like this...
http://www.screwfix.com/p/angled-radiator-valve-drain-off-15mm-x/70408

If you undo the "small square bolt" then water will drain from the hose connector underneath it. Use a spanner to loosen it.
The "flat tab sticking up vertically (underlying the plastic cover)" will turn off the water going into the radiator.
Where are you intending to add the Sentinel?

 

[swayzak]

I assume you're talking about something like this...
http://www.screwfix.com/p/angled-radiator-valve-drain-off-15mm-x/70408

If you undo the "small square bolt" then water will drain from the hose connector underneath it. Use a spanner to loosen it.
The "flat tab sticking up vertically (underlying the plastic cover)" will turn off the water going into the radiator.
Where are you intending to add the Sentinel?

Thanks

That's exactly what I have.

I have a funnel/tube and am planning to add to the radiator at the top (the hole covered by flat hexagonal head).

So I should turn off both valves connecting radiator to CH (the one on the drain-off & the one on the other side, by turning the plastic covers clockwise), drain off a couple of litres, close the drain-off tap, add the Sentinel, then open the valves again ?

 

[Armo74]

Depends what type of system you have? Combi?

 

[swayzak]

Depends what type of system you have? Combi?

No - 2004 Potterton Suprima 50 L, open system.

 

[swayzak]

Do I need a special tool to turn the "flat tab" when isolating the radiator ?

It looks like there should be a tap cover that would turn it, but the supplied plastic cover is just a cover & doesn't slot on to the tab.

The only thing I have that might work is some pliers, but don't want to damage it.


thanks

 

[45yearsagasman]

Pliers will do it, but don't you possess an adjustable spanner? Invest in some tools before attempting DIY work.

 

[swayzak]

Pliers will do it, but don't you possess an adjustable spanner? Invest in some tools before attempting DIY work.

Thanks

I have a set of spanners, but not an adjustable spanner. I'll get one.

If this is effectively a valve, why don't they just come with a tap cover so it can be turned on/off by hand ?

 

[45yearsagasman]

That one is the lockshield valve which is used to balance the flow through the rad and has a cap which will not allow further adjustment once it is fitted.

 

[StephenW]

What do you have at the other end of the radiator? If it's just a normal knob and not a Thermostatic Radiator Valve then you can just pull that one off and use it to turn the lockshield end. Otherwise it's spanner time.

 

[StephenW]

Oh, and before you go much further, your original premise is wrong. If you close both valves and then open the drain tap it will drain from the pipework and not the radiator. If you want to drain the radiator you will need to close both valves then loosen the joint between the valve and the radiator, catching the water in a shallow tray. Alternatively you need to tie up the ballcock in the expansion tank, drain some water from the pipework and add your Sentinel to the tank (then untie the ballcock!).

 

[swayzak]

*deleted*

 

[swayzak]

Oh, and before you go much further, your original premise is wrong. If you close both valves and then open the drain tap it will drain from the pipework and not the radiator. If you want to drain the radiator you will need to close both valves then loosen the joint between the valve and the radiator, catching the water in a shallow tray. Alternatively you need to tie up the ballcock in the expansion tank, drain some water from the pipework and add your Sentinel to the tank (then untie the ballcock!).

Thanks

Doing this via the radiator sounds a bit unnecessarily fiddly now !

So I should just tie up ball cock, open the drain tap to drain off some water (without having to mess around with those radiator valves) & untie ballcock ?

Unfortunately I have a slightly weird header tank (according to the plumber who fixed my heating recently).

It's a tank within-a tank - the large tank is hot water feed & within this there is a smaller tank which feeds the CHS.

I haven't seen it myself yet - is this likely to have a ballcock ?

 

[StephenW]

I can't picture what you're talking about but the cold water tank feeding the hot water tank and the feed and expansion tank for the central heating will be two separate entities otherwise you'd get the Sentinel chemicals getting into your water supply. Best you have a look in the loft and report back if it's still not clear.

 

[swayzak]

I can't picture what you're talking about but the cold water tank feeding the hot water tank and the feed and expansion tank for the central heating will be two separate entities otherwise you'd get the Sentinel chemicals getting into your water supply. Best you have a look in the loft and report back if it's still not clear.

I will do - but from what I've seen already there's a big black plastic tank next to boiler (hot water feed). Apparently in the bottom of this there is small 2nd plastic tank (the CH feed/expansion tank).

He already added some X200, but was concerned that is might be getting into hot water feed tank somehow as he noticed some bubbling in this when putting in X200. So he left the remainder ofX200 plus my full bottle of X100.

I don't use hot water to clean my teeth so, if this is the case, shouldn't do me too much damage I hope !

He said they used to do this sometimes (tank within tank), especially when room is restricted (as it is in my attic).