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General Chat Thread, Radiator / Central Heating advice in General; Looking for some help folks, Last few days we have noticed that our radiators are stone cold, despite there being ...
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    Gatt's Avatar
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    Radiator / Central Heating advice

    Looking for some help folks,

    Last few days we have noticed that our radiators are stone cold, despite there being (bloody) hot water..

    Now, I haven't got a clue about plumbing, but I have read a few forums that suggest bleeding the radiators might help, but it is more likely that we have a build up of iron Oxide sludge which needs to be flushed either with some sort of solution or by emptying the radiators completely (some even suggested removing them and using a hose pipe!)

    Can anyone offer some advise as to what we need to do?

    If it helps we have a back boiler and a hot water tank in the attic along with a cold waer tank..

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    I too am no expert, but a couple of other things to consider:

    Could be the pump has failed. Have a listen.

    Also, systems such as this sometimes have a 'summer valve', which shuts off the supply to the radiators - big red tap somewhere in the airing cupboard probably. Could someone have been fiddling with that?

    On the odd occasions I've had to deal with bleeding radiators, the symptom has been that the upper part of the rad is cold, but the lower and feed pipes are warm/hot. Also, has never (for me!) affected all rads at once.

    I don't know if sludge build up can suddenly kill your circulation or if it would degrade it over time . . . .

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    Gatt's Avatar
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    Quote Originally Posted by theriver View Post
    Could be the pump has failed. Have a listen.
    Think the pump is ok as I can hear a low humming / hissing in the background
    Also, systems such as this sometimes have a 'summer valve', which shuts off the supply to the radiators - big red tap somewhere in the airing cupboard probably. Could someone have been fiddling with that?
    We technically dont have an airing cupboard - the only "big red tap" is on the main gas supply pipe

    On the odd occasions I've had to deal with bleeding radiators, the symptom has been that the upper part of the rad is cold, but the lower and feed pipes are warm/hot. Also, has never (for me!) affected all rads at once.
    All rad's are stone cold.. will try bleeding one of the upstairs ones tomorrow see if it makes any difference...

    I don't know if sludge build up can suddenly kill your circulation or if it would degrade it over time . . . .
    This is what I am trying to figure out.. I suspect that if it can block one of the pipes, then it could.. also noticed that one of the rad's downstairs is leaking very slightly (its inky black) when you turn it on - the leak is right at the on/off valve - not sure if this is a dodgy valve or if its due to sludge...

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    creese's Avatar
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    If it is an old system and you have 'inky black' water leaking you may well have a problem. This is corrosion.

    Whilst its summer (yeh right) I would get a plumber in. The corrosion could ruin the whole system. The Plumber would flush out the system and refill with anti-corrosion additive. The worst case is that the corrosion can eat through the seams in the rad and you will have an awful mess to clear up, ruined paint work and carpets.

    I'm ex building trade and have seen this many times. The water from the rads should be near to clear, not black,

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    Gatt's Avatar
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    @creese - thanks for the info

    just to update on the inky black water leak - this is now running fairly clear - so not sure if it was a one off due to a bit of crap build up.... will check it again tomorrow..

    as for the plumber - relaly hoping i dont need to get one as i hear they can charge upward of 500!

    I have come across references to a solution that can be added to flush the system of sludge - but before i start messing with water, i wanna get an idea of what the best solution is..

    We have been in the house a few years an we dont really know much about rads as our previous house was all storage heaters / white meter... I am game to DIY it, but I don't wanna mess with water -especially CH - unless I know exactly what i am doing..

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    creese's Avatar
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    It will cost you for a plumber. It will cost you more if you flood the house.

    What do the radiators look like? Is there any blistering paint along the bottom?

    Back boiler and header tank are the simplest and one of the most inefficient and oldest systems. You need to turn the water to the header tank off, or tie the ball cock up securely to to stop it re-filling. Somewhere will be a drain cock at the lowest point. You can put a hose on here and drain the system. Then flush a few times then refill after adding the correct anti-corrosion in the tank.

    Simple if you know how but remember it is an old system and anything could go wrong. Like you and I an plumber will charge more to put right the mess you have got yourself into.

  7. Thanks to creese from:

    Gatt (8th June 2010)

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    Did a job like this the other week for my mrs's mum the other day, fix the leak (might just be able to nip it up to stop the leak) then bleed each of the rads starting from upstairs. The small leaks cause air to get into the system and can cause an air lock so the rads dont even heat at the bottom on some rads.

    IF all your rads are stone cold then check the flow and return pipes going to and from the boiler, if possible down to the pump (just cos its making a noise dosnt mean its working). There more like circulators than pumps if you know what i mean.

    Also there will be a motorised valve probably somewhere near your pump that directs water to your cylinder for hot water or your rads for heating sometimes they can stick, there is a small metal lever that sticks out the left side that you can use to open the valve manually. you should see this move when u turn on off the hot water at the controls.

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    creese's Avatar
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    Whiteknight639 some good points. Just to clarify a few things, it's not air but gas from the corrosion. Cold bottoms (on radiators) are usually due to sludge blocking the flow, cold tops usually due to air/gas.

    The valve was something I remembered after I switched. They can get stuck and pumps sometimes need bleeding too.

    Leaks should be taken very seriously as I have many radiators where paint and rust are the only thing between a heating system and a paddling pool in the lounge. The old radiators tend to rust along the bottom quite easily, newer radiators have no welded join on the bottom for this reason.

    Now you know why plumbers charge so much.

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    Gatt's Avatar
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    Well to further complicate matters.. they all came on this morning as scheduled... now i am really confused cos we switch the CH/HW on for a constant 3 hrs last night with not even a bit of warmth from them.

    It has also been suggested that I may have a stuck / sticking valve

    Might try bleeding them over the weekend see if there is any air in them, just to be on the safe side...

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    Some CH pumps have a plastic blanking plug with slot for screwdriver in the centre that when removed allows you to see if the pump impeller is turning. On an old one we had if the pump had stalled you could stick a screwdriver in the slot in the impeller shaft and turn it manually to get it going again (turn the power off before doing this!). I sometimes had to do this at the end of the summer because I forgot to run the heating for a short while each month to keep the pump 'free'.

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    If you drain & flush the system, be sure to add a corrosion inhibitor afterwards. There is a good forum on the Screwfix website where 'tradesmen' lurk.... they can be quite blunt with DIY users trying to do them out of business but you can pick up a lot of good tips, particularly about which products are good/bad....

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    Now I apologise if this is fairly obvious, but was there a difference in temp in the last couple of days? I know on ours (old systen) that the thermostat has been worn away and the covering is now loose and sometimes falls off. If you dont put it on properly it can look like the temp is set at 20 degrees but actually is more like 15. As a result the heating was either not coming on or turning off early.

    But then again, I know nothing about CH.

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    Quote Originally Posted by penfold View Post
    Now I apologise if this is fairly obvious, but was there a difference in temp in the last couple of days? I know on ours (old systen) that the thermostat has been worn away and the covering is now loose and sometimes falls off. If you dont put it on properly it can look like the temp is set at 20 degrees but actually is more like 15. As a result the heating was either not coming on or turning off early.

    But then again, I know nothing about CH.
    I think the main concern is that when bleeding a radiator the water should not be black. Now is the time to check it and flush through and add anti-corrosion. All batter than it breaking down in winter..... in 3 months time :-)

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    True enough

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    Turned my heating off at the beginning of May!

    I have the opposite problem - damn radiators upstairs get hot even thou the heating is off because the silly installers sometime in the 70's put a 22mm flow pipe but only a 15mm return pipe in, thus my hot water heating loop over flows into the Central heating header tank.

    People get really confused with heating and hotwater systems, but they are actually quite straight forward in most circumstances if you have a fairly traditional setup - it's basically 2 big loops with a header tank at the top - 1 for your hot water and one for your central heating.

    The most likely cadidate is the 3 port (or mid point) valve which will sit somewhere on the flow pipe from the boiler - this is responsible for directing the flow of water to your hotwater tank loop, central heating loop or both as dictated by the timer. You can easily see where the water's flowing by feeling the pipes (carefully - some of them will be very hot.) First make sure the system's running with only CH selected - it should only be diverting water to the CH pipes and none to the HW, if it is sending water elsehwere then you have a faulty 3 port value - this is what I would check first. You can then do the same in HW only mode and then select both. There's also normally an indicator on the side of the valve to show what it's doing - if you get someone to switch between HW and CH while you watch the valve you should see it move.

    They are surprisngly easy to change yourself, and the part is only about 50. I had to do this when I first moved into my house as mine was stuck on CH only mode and wouldn't heat the Hot water.

    Mike.
    Last edited by maniac; 9th June 2010 at 03:08 PM.

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