Combi Boiler vent Stains On Wall

Discussion in 'Misc DIY' started by Stuart, Apr 14, 2004.

  1. Stuart

    Stuart Guest

    My neighbour in the flat below has a combi boiler vented through an
    outside wall to the back of the flats . Earlier today I noticed that
    directly below the vent there was a reddish brown wet stain runing down
    the wall to the ground . It starts immediately below the vent . I have
    never noticed this before so it must be recent .
    Is it possible ( and in what circumstances) for water to come through this
    vent . I dont know how combi boilers work but do they need to be drained
    -presumably there might be occasions when the CH system has to be drained
    but again presumably,there would be an outlet for this water into an
    existing drain . Is it possible that someone has drained the system and
    put the draining hose out this vent to get rid of the water ??-cant see
    how THAT would be possible as the boiler will be sealed to the vent -won't
    it ?? .
    Stuart


    --

    "YESTERDAY is history,TOMORROW is a mystery,TODAY is a gift

    That is why it is called the present "
    Stuart, Apr 14, 2004
    #1
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  2. Stuart

    IMM Guest

    "Stuart" <> wrote in message
    news:...

    > My neighbour in the flat below has a combi boiler vented through an
    > outside wall to the back of the flats . Earlier today I noticed that
    > directly below the vent there was a reddish brown wet stain runing down
    > the wall to the ground . It starts immediately below the vent . I have
    > never noticed this before so it must be recent .
    > Is it possible ( and in what circumstances) for water to come through this
    > vent . I dont know how combi boilers work but do they need to be drained
    > -presumably there might be occasions when the CH system has to be drained
    > but again presumably,there would be an outlet for this water into an
    > existing drain . Is it possible that someone has drained the system and
    > put the draining hose out this vent to get rid of the water ??-cant see
    > how THAT would be possible as the boiler will be sealed to the vent -won't
    > it ?? .
    > Stuart


    Check if it is coming from the blow-off pipe, which is normally terminated
    below the flue to outside. If the pressure gets too high in the system the
    safety relief valve opens. The reddish brown is probably the colour of the
    water in the system. A fitter could have opened the relief valve to release
    pressure. Check this out.

    The blow-off pipes should be terminated a few inches from the outside floor
    level, with an elbow facing the wall. If it blows then it hits the wall at
    the bottom. If it is terminated at high level it could spay boiling water
    on someone beneath.

    If it is the blow-off pipe then get him to run it down the wall. Also get
    them to clean the wall.
    IMM, Apr 14, 2004
    #2
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  3. Stuart

    John Rumm Guest

    Stuart wrote:

    > Is it possible ( and in what circumstances) for water to come through this
    > vent . I dont know how combi boilers work but do they need to be drained


    If it is a condensing boiler (many recently installed high efficiency
    boilers will be) then you would expect allot of water vapour to come out
    of the flue. You will normally see this as a quite visible plume of steam.

    When the boiler is installed the flue should be installed at a slight
    angle through the wall - such that it runs "uphill" from the boiler (a
    slope of one to two degrees is usually enough). Hence any moisture that
    condenses in the flue before it gets outside should run back down the
    inside of the flue and into the boiler.

    If its is a condensing boiler, and, the flue looks like it is horizontal
    (or worse sloping down), then that could be the problem - although it is
    probably unlikely to be reddish brown itself you may find it is
    discolouring the wall due to its slight acidity.


    --
    Cheers,

    John.

    /=================================================================\
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    John Rumm, Apr 15, 2004
    #3
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