Changing a radiator tail - Drain down or not?

Discussion in 'Plumbing and Central Heating' started by SproutsDad, 11 Sep 2015.

  1. SproutsDad

    SproutsDad

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    I have a hallway double radiator in a tight space at the foot of the stairs behind the front door, set a long way off the wall hanging on the longer side of the offset wall brackets. It also has vertical 15mm tails coming out of the floor some 120mm away from the wall which frequently get kicked because they stick out into the floor space. This must have been driven by a floor joist positioned 70mm parallel to the wall and right in the way of where pipes would normally come up vertically to the radiator.

    The radiator has already been removed for decorating so the 15mm tails are easily accessed and beneath the floor they go to a 15mm to 8mm microbore compression reducing joint that is easily accessible, the pipework from there onwards underfloor is 8mm.

    PLAN >> So I now want to get the radiator back on the shorter side of the brackets gaining about 18mm. Also to move the tails to sit inside the space between the wall and the joist. They would need to be remade with a dog-leg bend to reach the radiator, but it should all look neater and be less of an obstacle. My plan would be to remake the section of 15mm tail and just swap it over at that same joint.

    However >> I have had problems with air in this Vaillant Thermo compact based sealed heating system. But the faulty pressure gauge and auto-vent valve have been replaced and the problem resolved via a good heating engineer. So I don’t want to now have to drain down the whole system to do what is hopefully a simple task and potentially introduce more air lock problems!

    Question >> Can I get everything ready with new threaded nuts and olive in place and swap them over with loss of just some water, or am I risking disaster? No I don’t have access to a freezing kit or know how/ if I can isolate and minimise any water loss. Should I let just some water out of the drain valve to ease the pressure and make it easier to work with?

    Would I just be introducing lots of air into the system and be better off draining the whole thing anyway? After all this is downstairs and if it doesn’t go to plan there could be a lot of water?

    Please advise the best route.

    Many thanks.
     
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  3. SproutsDad

    SproutsDad

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    Same query, better explained .... Reading my own post above, perhaps it doesn't read very clear, a sketch should help ?

    A hallway double radiator that I want to pull in closer to the wall and run the tails coming from the floor, behind instead of in front of the floor joist.
    The tails will be bent dog-leg as shown on sketch to align with radiator valves.
    >> Can I do the swap from old to new tails using existing compression reducers 15 to 8mm, without draining the whole system down again? Or is it too risky?
    upload_2015-9-11_19-15-56.png
     
  4. kittedup

    kittedup

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    You should be fine if you only have one open end at a time.

    I would do it like this:

    Isolate rad, drain and rehang
    Close any air vents on system
    Open one rad valve and release system pressure. You will then find out of the system will "hold". You'll probably get about a litre or so of water.
    Make the changes to that side of the pipework and close off rad valve.
    Repeat other side.
    Open air vents, fill system and bleed rad.
    Drink coffee.

    Ted
     
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  5. You will be working in the floor space downstairs anyway so a little water shouldn't hurt. Just get all you fittings and pipe ready in advance.
     
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  6. SproutsDad

    SproutsDad

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    Thanks kittedup and squeaky.
    The rad is already off the wall for decorating so I just have 2 tails out from the floor.
    I had intended using the the drain off valve which is on the tail by the front door, but without the rad it would need blanking off on the rad side otherwise it will squirt everywhere when opened.
    But if I do as you say ...........
    .... then I shouldn't need to do that, or shall I open the drain valve (same thing?) and let some off from there as a start?

    What if the system just keeps running? Should I just do that final compression connection quickly holding as much back as possible? As you say ....
    See circled elbow below>>

    Will it matter using a compression elbow on the new tails below the floor?
    Or should this be a gentle bend with no elbow?
    >>> Also. Would you be doing this at all based on what I have described, just to pull a rad and its tails in closer to the wall?
    >>> Or would you have left it? See Now and Proposed in sketch in earlier post << Your opinion, just for my curiosity please!

    Many thanks to both.
     
    Last edited: 12 Sep 2015
  7. SproutsDad

    SproutsDad

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    Elbow as circled below, or a gentle bend instead?
    upload_2015-9-12_11-31-5.png
     

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  8. kittedup

    kittedup

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    Bend is better which you can do dry before you start all this.

    Ignore the drain off. Turn off system. Open one valve over a tray and wait for the water to stop. If it doesn't stop, you're into a full drain down. Chances are it will though.

    Definitely worth doing

    Ted
     
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  9. I find it helps to shut off all the other rad valves first (make a note of positions for balancing).
     
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  11. SproutsDad

    SproutsDad

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    Thanks for the advice.
    I have tried bending a sample of the proposed dog-leg 'S' bend radiator tail using a pipe spring and bending it over a 4" dia round wooden post.
    This is what happened! ............. the one on the right is particularly bad.

    upload_2015-9-12_17-47-31.png
    I have bent things like this previously and had to really push, this went easily , too much so, which I assume is down to what seems to be thinner copper tube.
    I can practice more but it could get expensive with copper currently at £3,471 per tonne and me a slow learner!!
    What am I doing wrong? Is the copper tube really thinner than some few years ago? It feels like it is.
    Any advice much appreciated, thanks.
     
  12. St0rmer66

    St0rmer66

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    Those will work fine, just don't look as good.
     
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  13. AlanE

    AlanE

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    If you have 8mm main pipe to radiator why not extend this in 8mm bring it up behind joist and you can bend it to required position easy by hand.

    Either replace rad valves with 8mm ones or us a 8 to 15mm adapter with existing valves.
     
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  14. SproutsDad

    SproutsDad

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    AlanE.
    Thanks but that in 8mm was exactly what I had and was trying to get away from because it got kicked and knocked and was forever weeping requiring tightening and tweaking.
    I put ina replacement rad with these new 15mm tails on the wrong side of the joist because it was more difficult to bend these, but the radiator is a long way out from the wall and the whole thing being at the foot of the stairs I get a similar problem with it all being in the way, but without the leaks - 15mm is more robust. This was an attempt to pull it all back snugly into the wall.
     
  15. AlanE

    AlanE

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    So 8mm clipped to skirting board itself 90° elbow under valve back to skirting? Or, depending on skirting height and radiator height, bring 8mm up behind skirting.
     
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  16. SproutsDad

    SproutsDad

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    I was trying to make it more robust by having 15mm instead of 8mm above floor, the only hiccup was this dog-leg tail bend in 15mm.
    Sounds like you think it is better to get back to 8mm for the whole run but routed snugger and less exposed.
    >> Is that instead of mixing 15mm above floor and 8mm below?
    >> Would that be your favoured option from where I am now?
     
  17. SproutsDad

    SproutsDad

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    St0rmer66
    Q> So what was the issue with the bending shown in photos? Is it down to the thinner copper tube, or me, or both?
    I didn't get this problem some few years ago with what then seemed to be thicker 15mm tube.
    Thanks

    [​IMG] upload_2015-9-13_11-0-17.png
     

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