Radiators, bottom of the rad not getting hot

Sounds like a build up of sludge in the bottom of the radiator. Tomp and the boy plumb, will be along shortly to advise further.

 

yes thats a sign of bad circulation or uneven distrubution of the hot water coming from the boiler, try balancing first, ( what's that i hear you think) , hang on a mo I'll pop a video on,

 

Tom - thats another great video, very helpful.
Thanks!

 

It does sound like a build-up of hard-packed sludge in the bottom-centre of the rad. This build-up simply stops the water flow over that area. It might get warm after a good while, but this will be due to conduction, but the bottom-centre will never be actually 'hot' if it's blocked.

You can check whether instead it's a 'balance' issue by shutting off the other rads and seeing if a previously 'cool' rad now gets very hot very quickly and all over. Does it?

Ok, assuming it doesn't, AshMiah, are you up for a spot of DIY?

Messy DIY...?

Choose one of the miscreant rads and shut off the two valves fully. Get a flattish container that'll slip under the rad valve, and have plenty of cloths ready too. Undo the large chrome nut on the valve where it starts heading into the rad itself. As soon as you loosen it, water should start to dribble out.

Depending on how brave you are, you can either let it trickle really slowly like this - it'll take a half-hour to drain - or you can open that nut fully in which case you better be ready to catch and transfer that water as the pan fills.

Undo the bleed vale at the top too so's air gets in.

Ok, once the rad is empty (but there will still be some real nasty black water in it...) remove the other end's nut too so's the rad can be lifted straight up off its brackets and taken outside.

Watch the mess...

Ok, outside shove a hose into one end of the rad and turn on fully - look out for what's coming out t'other end. I'm guessing it'll be yucky.

If you have a single-panel rad, there's a chance the hose will fire straight through and act directly on the crud inside. If it's a double-panel, or one with 'cranked' ends, the hosing won;t be as effective, but should hopefully still do the job. Turn the rad upside-down and give it's bottom a goodly thumping with a rubber mallet - see if that releases any crud.

Ok, if it happens that lots of black gunge does get flushed out, then you know what your problem is, and the best thing is to repeat this horrible process on all the other rads - definitely on the cool-bottomed ones.

Then replace them all, open the valves, refill, bleed the air and top up you system if it needs topping up.

With one rad, add a hefty dose of powerful cleaner such as Sentinel X800, and also fit a dual-action filter on the return pipe to the boiler.

Run it as normal like this for a couple of months, checking and cleaning the filter every fortnight.

Of course, if the rad and the water turns out to be clean, then it's a different cause like the system needing balancing.

 

What we gave was 'advice'.

Ash, a Magnaclean does work to remove 'magnetic' sludge, and possibly non-magnetic too depending on the model - I've chust bought an upgraded sleeve for my Magnaclean Pro which is meant to catch the non-magnetic stuff too.

But, the gunge has to be in the water before it can be caught, so that means having cleaning chemicals added to the system - like X800 for a couple of months. If there are no cleaning chemicals, then the gunge will largely stay put in the rads and pipes.

The reason for trying the "shut off all rads except the cold rad's one" is not to force the gunge out (tho' it might...) but simply to check if it is a problem down to gunge, or whether that rad chust ain't getting enough flow.
Ie - is it 'a Question of Balance' (an ok Moody's album, but not nearly their best).

So, to shut off the flow to other rads to stop them working, you only need to shut ONE valve on each, and that should be the control valve - the TRV or temp-adjusting one (NOT the lockshield.)

I should have mentioned; before you touch the other end - the 'lockshield' valve - on any rad, count the exact number of turns/part turns it takes to close them off, and note this on a piece of paper taped to each rad. Put a spanner on it and note which way the handle is pointing - you need to note stuff like "one full turn and 2 o' clock" or summat. (It could easily be less than one turn, so beware - it's pretty critical...)

That 'first' rad wot's behind the couch (and affecting it... ) needs that 'lockshield' closed off even more than you've done already - simple as that. The other end - the control knob end - should be left fully open while you do this. The point of balancing is to get that rad heating up at the same rate as the others when they all have their control knobs fully open - only then will the lockshield tweaks make sense.

(And that rad doesn't have a TRV because I assume the wall thermostat is in that room?)

So, give that rad's lockshield a 1-hour clockwise turn. (As in one-hour on the clock...) Obviously you don't close it fully - 'cos guess what? Yes, it'll stop working. But you do need to close the lockshield a touch more. And possibly a touch more. Perhaps even a touch more.

Didn't we mention that balancing a system is a pain-staking task?

What model of Magnaclean do you have - is it the full-sized 'Pro' model? If so, perhaps it's worth looking for the upgrade sheath - they are available from our hosts (and on fleabay for a bit less...) Drain the body (use a short tube to syphon it out) and fill with X800. Run the CH for 30 seconds to get that dose into the system, and add the remainder of the bottle.

 

The valves at each end can be the same, except they should at least have different 'tops'.

The exception to this is if any rads have TRVs on them - which they should (except for the room with the 'stat).

If the valve bodies really look the same, do the white valve tops also look the same? The lockshield should have a smooth tall white cap that doesn't do anything when you turn it - it has to be pulled off to reveal the spindle underneath which is what you need to turn.

The 'control' valve should have a wider white plastic top which is fitted tightly on to the spindle, most likely with a screw going down from the very top. It should have obvious 'grips' to make it easier to turn, and it should turn the spindle when you operate it.

Don't you have TRVs on any of them?

Traditionally the 'flow' to the rad went to the 'control' valve, whether manual or TRV. So the lockshield went on the return. But with manual valves, it doesn't really matter, so you can't necessarily tell from this. Even TRVs these days can go on either.

So, please double-check and see if the two valves are really the same.

To recap 'balancing'; the idea is that, with all the rads having their control valves/TRVs fully open, they should all heat up to 'hot' at roughly the same rate. So, as you say in your second paragraph, the idea is that any rad that heats up much faster than the others should have their lockshield tweaked down a wee bit.

All this is done with all rads having their 'control' valves fully open.

You then need to wait and allow the rads to settle. Don't tweak down a 'fast' rad and also tweak open a 'slow' one - because tweaking off the fast will should automatically allow more water to go to the slow ones

Ideally you should have a couple of rad thermometers, one clipped to the flow pipe and one to the return - you then teak to get a 11oC drop in temp across the rad, I believe.

But, I think you can start from the premiss that your rads have been balanced reasonably well at the start, so all you are doing now is fine-tuning.

AND, if any rad has gung in it - which is quite likely - that will be the cause of it being cool, so balancing should not be done as a 'cure' for this.

Really - you do need to check a 'cool' rad and find out once and for all whether it is full of s***. Because that will determine the next course of action.

Fort instance, if the rads DO have sludge in them, you need to clear it - it will almost certainly land you with a huge bill for sorting your boiler in a couple of years time.

And, if the rads do have sludge in them, you might want to try and clean them over time one at a time by fully opening both valves on that rad to give max flow. So note down the lockshield position before you start.

Your lounge sofa - once you balance that rad by probably closing off the lockshield so it gets hot at the same rate as the others, then you control its temperature by turning down the control valve. You can make the rad whatever temp you want by doing this, including 'luke warm'. But the lockshield should stay put once set.

Your sparky seemed to have a thing about having the wall stat in the hall... This can be ok, but it's usually positioned in the sitting room. Please note that the rads in the room with the 'stat should NOT have TRVs fitted, but all the other rads SHOULD.

Also note that if you manually turn down the rad behind the sofa, this could make that room cooler so that the wall stat will take longer to be 'satisfied', so the heating will be on for longer.

Anyways, if you reckon you can turn down that 'sofa' rad to protect the sofa whist still heating up your room nicely, you should be fine.

Yes, the X800 is boiler-friendly. You can chuck it in as you say - it'll take a couple of fills of the filter to get it all into your system, and if you have discovered that you DO have filth in there, consider adding a double-dose and leave it in for a couple of months.

Then drain down and flush through your system, refill with X100 (inhibitor) and X900 (permanent cleaner), and live happily ever after.

I hope this is my last word on this 'cos my two fingers are hurtin'...

 

Cool - keep us posted