One radiator not getting warm (yes, that classic) - Hopefully fixed?

Discussion in 'Plumbers' Talk' started by HarryCrumb, Sep 3, 2021.

  1. HarryCrumb

    HarryCrumb New Member


    This is a little bit long, but in case my issue isn’t solved, at least all the info is here. My main questions are numbered at the end.

    I’ve just been through an awful lot of problem solving to try and fix a radiator that wouldn’t get hot. A couple of times I thought I’d found the solution, only to realise I had not. I’m really hoping that I now have solved the issue, I just need to refill to confirm it. Because during the long process of elimination I shut all the lock valves, and because I hope this is the last time I have to refill the system for a while, I want to get some decent advice on filling without airlocks, and balancing.

    The radiator is on the ground floor, the last on a four rad leg. It’s probably the furthest from the combi (Vaillant EcoTek plus) which is on the first floor. After two bedrooms, the pipes come down the wall to the living room radiator. Here they go in to speedfit three way connectors, which changes it to microbore copper to the living room rad, and microbore plastic tube going off and slightly up (one step up) to the kitchen rad.

    I’d been through checking pins, valves, flushing the rad, using a larger bore to bleed with… I could see that there was hardly any force in the flow pipe. Eventually I go to the last thing I wanted to do, cut the floor boards in the living room (it’s glued and varnished/no carpet) and lift the step to check for a blockage. Under the step, the plastic tube joins to copper microbore, which goes a couple of feet under the floor to the rad.

    Anyway, the flow section was absolutely packed with black silt. It took me quite long time with a straightened coat hanger and and large syphon pump filled with soapy water, but I eventually got it cleared. The return section was fine but I made sure it passed clear running water.

    I think that the previous owner had the system serviced properly because there are Fernox stickers on the Combi, and the fluid that came out when I first drained it was clean enough. I’m guessing that the build up of sediment was because a) it’s the lowest point of the house, and b) the microbore tubing is just asking for trouble.

    So, I’ve put it all back together and am ready to give it a test. Here’s my main questions;

    1) To really avoid an air lock, is it a good idea to bleed the radiators in any particular order? The way I’ve been doing it is to fill up to just over 1bar, then start with the lowest, and work my way up the house. And I'm wondering what position the valves should be in. If it was balanced, I would obviously leave the locks alone.

    2) Should I start to balance only after all the air has been bled from the system?

    3) the lock valve in the kitchen leaks a little bit, so once this problem is solved I’m going to replace it. I see there are loads of valves on screwfix, so how do I choose?

    4) for the following house, would a 500ml tub of inhibitor be enough? I know thats hard to say... I'm not sure how many litres is in my system. I've got the following;

    1 x large rad
    3 x med
    2 x small
    2 x large towel

    Thanks for any help! Very much appreciated!

  2. terrymac

    terrymac Screwfix Select

    Fill to 1bar ,bleed downstairs rads first,in any order.
    Do balancing after all air is removed.
    Pick any lockshield they all do the same job,and fit it before filling system.
    500ml is enough.
    Consider running a cleanser in the system ( follow makers instructions), before finally adding inhibitor. And if you don't already have one ,fit a filter
    HarryCrumb and pppmacca43 like this.
  3. pppmacca43

    pppmacca43 Super Member

    Always handy if u can have a hand from someone when filling, they can stay at the filling loop and keep it at 1bar by turning the valve on and off as needed, saves you keep having to go back.
    Pretty much agree with everything terrymac says, he’s answered it well, start at lowest point and work your way up, venting the highest radiator or towel rad last.
    Definitely consider getting a magnetic filter fitted on the return to the boiler if u can, you’ll be amazed how much it will pick up. 500ml should be enough inhibitor, different brands treat different amounts of litres tho, if in doubt add an extra bottle, it won’t hurt.
    When balancing open the furthest lock shield valves fully open, as u get closer to the boiler they can be closed more. I suspect if u had a blockage it will all flow well now it’s been cleared.
    When replacing the leaking lock shield valve I would go for Drayton, a good brand, there lockshield valves can be a bit stiff I find but they are good quality.
    Last edited: Sep 3, 2021
    HarryCrumb likes this.
  4. HarryCrumb

    HarryCrumb New Member

    Brilliant answers, thanks very much! I'll post back in a day or two to update.

    Oh, and I will certainly look at fitting a filter after seeing what came out of that pipe!
    Last edited: Sep 3, 2021
  5. HarryCrumb

    HarryCrumb New Member

    Just one thing... Am I correct to think that a cleaner should be in and circulating for a few days or a week, before being drained, right? I can add some tomorrow, then when I drain that out, I should have acquired a filter. Would be good timing.
  6. pppmacca43

    pppmacca43 Super Member

    Yeah that is normally fine although check on the instructions for whatever cleaner you get for the maximum amount of time they can be left in the system. Ideally u would want your magnetic filter in first, so it can catch all the crud being broken down and moved about, but after should be ok. Make sure u flush the system thoroughly.
    HarryCrumb likes this.
  7. HarryCrumb

    HarryCrumb New Member

    Ok, that makes sense. Thanks!
  8. HarryCrumb

    HarryCrumb New Member

    Does anyone have a favourite filter for fitting in to small places? This is an old house (late 1800's) and while the work thats been done wasn't bad, it's not great. The return pipe is about 12mm from the wall, so no fancy pipe cutter for me. Awkward junior hacksaw blade more likely.

    I've been looking at the Fernox TF1 Omega, but because it drains from the bottom, it could make life difficult. I have seen a video where the guy turns it horizontal to flush it out. Is it bad that you can't actually ever get inside to clean it?

    I'm also looking at the Magnaclean Atom which seems easier to service, but lots of people saying it's overpriced. And it might be too deep for this space.

    The issue is more with depth than height. I've got about 120mm from the centre of the pipe, out to the panel. It could angle to one side though. I might have to buy a couple of filters and return the one I don't use.

    Looking at the photo, the return pipe is 2nd from right. All the tiles are ripped out from having a new gas pipe installed (now comes through the wall). Old gas pipe beneath that can be cut out for space. Also, there is a T section on the return that goes to a flexi hose. Thats not in use so I'm thinking cut that T section out for the filter and loose the flexi bit.

    When I put it back together I'm thinking of a removable panel instead of tiles. It was all a bit too permanent. That isolator switch will be moved as well.

    Any suggestions of filters would be appreciated! Thanks

    Last edited: Sep 4, 2021
  9. HarryCrumb

    HarryCrumb New Member

    Update; I've ordered the Fernox TF1 Omega, without valves. It's the only one I can find that will (hopefully) fit, and I can't find a bad review about it. I may have to fashion a flexi hose for flushing it. I've ordered the F3 cleaner and so hopefully it will all come in to stock on Monday.
  10. pppmacca43

    pppmacca43 Super Member

    Not used the tf1 omega before. All the ones I’ve used have valves so u can shut them off and clean them. Would be worth if u can fitting a valve below it, even below that tee if u need to. What’s the tee for? Looks like a filling loop on it but there is a filling loop on the boiler, if so u could cut out that tee?
  11. HarryCrumb

    HarryCrumb New Member

    The T may have been a filling loop but it doesn't look like it's been used in a long time. Certainly long before I moved in, about ten months ago. As you say, the active filling loop is on the boiler.

    The filter needs 75mm cut out, and I'm planning on cutting out that T. There is a version of the TF1 Omega with valves but it would be very tight in there, and would make servicing the boiler very difficult. If I ever need to service the filter I'll have to drain the system, but it's not a big task.
  12. HarryCrumb

    HarryCrumb New Member

    I got the filter fitted. Made sure everything was water tight, then added the F1 cleaner via the towel radiator on the top floor. It says you can flush after one hour, or leave up to a week for systems with more sludge. It's difficult for me to know how bad it is. It's the three downstairs radiators that feel less hot along the bottom edge. First and second floors all feel very equal.

    Unless anyone suggests something different, I'm just going to keep checking the heat distribution every day and see if it improves. I won't leave it any long than a week though.
  13. Chewy

    Chewy New Member

    Did that do the job Harry?
  14. Jimbo

    Jimbo Screwfix Select

    When flushing out you need to keep rinsing through with fresh water until the TDS reading is within 10% of clean tap water. TDS meters are available on Amazon pretty cheap.
  15. HarryCrumb

    HarryCrumb New Member

    I think so. A bit tricky to say without x-ray vision but all the rads are piping hot at the top and the house feels well heated. On to the next job now...! : )
    Chewy likes this.
  16. HarryCrumb

    HarryCrumb New Member

    I just flushed till everything looked clean/clear. The boiler is due a service next year so I might have the system flushed for good measure.

    Just while this threads been bumped, is it ok to mix fernox prohibitor with an other brand? I bought some other brand prohibitor for a towel rad that isn't on the CH and I'm just wondering if that could be used if I needed to top up the house system. Always good to know these things...

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