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Very slight leak from towel rail connection point

Discussion in 'Plumbing and Central Heating' started by Giles Mann, 21 Apr 2020.

  1. Giles Mann

    Giles Mann

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    I have found that the towel rail radiator connection leaks very slightly.

    It doesn't drip, it is just slightly wet at the points shown in the photo. The leak is so minor that I am not getting any noticeable pressure loss in CH system.

    What approach is best to take?:
    1. Do nothing as leak is not affecting system
    2. Try and tighten the nuts
    3. Drain towel rail, remove it and add PFTE tape before re-installing

    Thanks
     

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  2. oldbuffer

    oldbuffer

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    A. In the current situation, option 1.
    B. When things free up a bit, try option 2. Make sure the valve cannot rotate while tightening. Do the top nut first, it may be leaking and letting water run down over the lower one.
    C. No point adding PTFE tap, the seal is not on the threads.
    D. It doesn't look like it, but it is possible the leak is where the tail goes into the radiator. If that is the issue you will have to empty the radiator, remove the tail, re-wrap with more PTFE (or Loctite 55, or use Flomast pipe sealant) and screw the tail in again.
     
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  4. Giles Mann

    Giles Mann

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    Thanks oldbuffer. I'll leave it until things go back to "normal"

    I'm trying to get my head around how these connections work. I have been googling and found out about olives - not really sure how they would be water tight by looking at them!
    I've added a sketch showing where the water is exactly and what I think each connection is like - my assumptions might well be wrong.

    Would not one side of the each nut have a seal that is based on the threaded part of the valve or am I missing something?

    Yea I checked for water at this point and nothing. There was a tiny amount of water at the top of the nut though.
     

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  5. oldbuffer

    oldbuffer

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    1. An olive is a ring of brass or copper. The inside diameter is a plain flat, the outside diameter is convex.
    2. The edge of a compression fitting and the inner diameter of the corresponding nut each have a bevel angle.
    3. The nut is put on the pipe, the olive added and the assembly slipped into the fitting.
    4. When the nut is tightened onto the threaded outside end of the fitting, the olive is squashed between the two bevels.
    5. This squashing tightens the inside diameter of the olive onto the pipe, and the outside of the olive into the two bevels.
    6. It is this squashing which causes the joint to become water tight.
    7. Threads never seal well enough to be watertight unless they:
    7a. Have some substance between them which fills up the gaps.
    7b. One side (the male) thread is cut on a taper, so that the further it mates, the tighter the seal becomes. Even so it is normal to use a sealant of some sort.
     
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  7. Giles Mann

    Giles Mann

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    Fully understand now. Thank you very much.

    I didn't know it was called a compression fitting which is probably why my googling wasn't being very successful.
     
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