Combi Boiler Pressure Drop

Discussion in 'UK DIY' started by Phil Richards, Nov 18, 2005.

  1. First of all I know very little about boilers, so please be patient!

    Having got a decorator to remove and drain out a radiator so as he could
    paint behind it, on reconnecting and turning the hot water inflow back on,
    we noticed the pressure on the system drop from about 1.2 to almost zero.
    This didn't surprise him as basically we took out a fair proportion of the
    water in the system (total of 4 radiators in our flat).

    Problem is now we can't see away of replenishing the water back in.
    Examining the pipe work underneath the boiler, the chap helping me saw that
    the two pipes to the RHS of the photo below should be connected by the
    flexible silver pipe just hanging over it!

    <http://www.philrichards1.pwp.blueyonder.co.uk/Boiler.jpg>

    At that point he gave up and said to get expert advice! Fortunately we have
    a fixed service contract with British Gas who only 7 months ago carried out
    a service check and presumably this didn't appear out of the norm. They are
    due out Monday morning.

    On speaking to someone else, from my descriptions he reckoned the system is
    sealed. There is no water tank in the loft, all water comes in from the
    mains and he reckoned sometimes once a boiler like this is set up and the
    system filled up with water, often the water supply is disconnected.

    So my questions are:

    1. The boiler seems to run OK on a much lower pressure, with the radiators
    at their normal heat. The only difference is you can hear air in the
    system. Is it safe to keep the system running this until the engineer comes
    out Monday, especially as the current cold weather is forecast for the
    weekend?

    2. How on earth is a system supposed to be refilled easily when radiators
    are drained out? Or is there another way of allowing mains water into the
    system.

    3. How easily would it be for the engineer to get the pressure back? I only
    hope that especially as British Gas have already examined the system (on
    two occasions, once after it developed a fault, the other a service check)
    they will not say I've tampered it or it is a design fault.

    Many thanks.

    --
    Phil Richards
    London, UK
    Home Page: http://www.philrichards1.pwp.blueyonder.co.uk
    Phil Richards, Nov 18, 2005
    #1
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  2. Owain wrote:

    >> <http://www.philrichards1.pwp.blueyonder.co.uk/Boiler.jpg>
    >> 2. How on earth is a system supposed to be refilled easily when radiators
    >> are drained out? Or is there another way of allowing mains water into the
    >> system.

    >
    > By connecting the flexible silver pipe between the cold water main and
    > the radiator circuit, and turning the taps on until the pressure gauge
    > goe up to <whatever it should be>.
    >
    > Are you saying there are now no screw-on connection points for the
    > flexible pipe?
    >> 3. How easily would it be for the engineer to get the pressure back?

    >
    > Very easy assuming there are screw-on connection points for the flexible
    > pipe. I don't know what British Gas will say - be prepared for them to
    > tell you you need a new boiler.


    Perhaps not too clear from the photo I took, there are screw on connections
    on both pipes on the RHS. I can see now how easy the job will probably be.
    What I don't understand is why they effectively got sealed off presumably
    after the boiler and radiator system were installed making it difficult to
    top it up after, say what I did, by draining out one radiator.

    > I don't know what British Gas will say - be prepared for them to
    > tell you you need a new boiler.


    Well I hope not.....

    --
    Phil Richards
    London, UK
    Home Page: http://www.philrichards1.pwp.blueyonder.co.uk
    Phil Richards, Nov 19, 2005
    #2
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  3. In message <>, Phil Richards
    <> writes
    >Owain wrote:
    >
    >>> <http://www.philrichards1.pwp.blueyonder.co.uk/Boiler.jpg>
    >>> 2. How on earth is a system supposed to be refilled easily when radiators
    >>> are drained out? Or is there another way of allowing mains water into the
    >>> system.

    >>
    >> By connecting the flexible silver pipe between the cold water main and
    >> the radiator circuit, and turning the taps on until the pressure gauge
    >> goe up to <whatever it should be>.
    >>
    >> Are you saying there are now no screw-on connection points for the
    >> flexible pipe?
    >>> 3. How easily would it be for the engineer to get the pressure back?

    >>
    >> Very easy assuming there are screw-on connection points for the flexible
    >> pipe. I don't know what British Gas will say - be prepared for them to
    >> tell you you need a new boiler.

    >
    >Perhaps not too clear from the photo I took, there are screw on connections
    >on both pipes on the RHS. I can see now how easy the job will probably be.
    >What I don't understand is why they effectively got sealed off presumably
    >after the boiler and radiator system were installed making it difficult to
    >top it up after, say what I did, by draining out one radiator.


    I understand that it is correct for the silver tube to be removed but,
    usually, you can just screw it back on and open the taps to fill the
    system.

    Are the pipes capped and sealed? Or will the caps pop off to allow you
    to screw the pipe on?

    --
    Richard Faulkner
    Richard Faulkner, Nov 19, 2005
    #3
  4. Phil Richards

    John Rumm Guest

    Phil Richards wrote:

    All the information and some background as to how your system works can
    be found here:

    http://www.makewrite.demon.co.uk/SealedCH.html

    > So my questions are:
    >
    > 1. The boiler seems to run OK on a much lower pressure, with the radiators
    > at their normal heat. The only difference is you can hear air in the
    > system. Is it safe to keep the system running this until the engineer comes
    > out Monday, especially as the current cold weather is forecast for the
    > weekend?


    Depends on how low the pressure is... some boilers will refuse to fire
    without enough in the system. Sounds like yours is running OK though.

    > 2. How on earth is a system supposed to be refilled easily when radiators
    > are drained out? Or is there another way of allowing mains water into the
    > system.


    Via the "filling loop" (i.e. that hose of yours). There are two
    connection points: one is a tap - this is on the cold main supply. The
    other is a non return valve on the heating system. This lets water into
    the heating system but not out.

    The only slight extra wrinkle with your setup is it looks like someone
    has screwed caps onto the filling loop connection points. This is no bad
    idea since it keeps dust and other crud out of the ends of the valves
    etc. You should find the caps unscrew easily by hand. No water should
    come out when you take the caps off.

    It is "correct" to disconnect the filling loop once the system is
    filled. (basically it is another safeguard that prevents any possibility
    of contaminanted dirty water out of your heating system getting back
    into the drinkable mains supply)

    > 3. How easily would it be for the engineer to get the pressure back? I only


    Very easy. Connect up the loop and open the tap. Watch the pressure
    guage and turn off when at the right pressure. Bleed any air from the
    radiators. Top up the pressure if neccessary. Repeat until there is no
    more air to bleed. See the FAQ for a full description.

    > hope that especially as British Gas have already examined the system (on
    > two occasions, once after it developed a fault, the other a service check)
    > they will not say I've tampered it or it is a design fault.


    No, your system looks fine. Topping up the pressure is one of those
    tasks that you will usually only need to do should you remove rads etc.


    --
    Cheers,

    John.

    /=================================================================\
    | Internode Ltd - http://www.internode.co.uk |
    |-----------------------------------------------------------------|
    | John Rumm - john(at)internode(dot)co(dot)uk |
    \=================================================================/
    John Rumm, Nov 19, 2005
    #4
  5. In article <>,
    Phil Richards <> writes:
    > Perhaps not too clear from the photo I took, there are screw on connections
    > on both pipes on the RHS. I can see now how easy the job will probably be.
    > What I don't understand is why they effectively got sealed off presumably
    > after the boiler and radiator system were installed making it difficult to
    > top it up after, say what I did, by draining out one radiator.


    The filling loop must be disconnected when not being used.
    This is to prevent any remote chance of the radiator water
    getting back into the fresh water supply. I can't see clearly
    in the photo, but the supply end should have a tap and the
    heating end should have a one-way valve to prevent water
    coming back out.

    --
    Andrew Gabriel
    Andrew Gabriel, Nov 19, 2005
    #5
  6. John Rumm wrote:

    > Phil Richards wrote:
    >
    > All the information and some background as to how your system works can
    > be found here:
    >
    > http://www.makewrite.demon.co.uk/SealedCH.html


    <snip>

    > No, your system looks fine. Topping up the pressure is one of those
    > tasks that you will usually only need to do should you remove rads etc.


    Many thanks to John, Owain & Richard for all their help. I must say out of
    the many newsgroups I read this seems to be one of the friendliest & most
    helpful!

    --
    Phil Richards
    London, UK
    Home Page: http://www.philrichards1.pwp.blueyonder.co.uk
    Phil Richards, Nov 19, 2005
    #6
  7. Phil Richards

    Guest Guest

    On 19 Nov,
    (Andrew Gabriel) wrote:


    >
    > The filling loop must be disconnected when not being used. This is to
    > prevent any remote chance of the radiator water getting back into the fresh
    > water supply. I can't see clearly in the photo, but the supply end should
    > have a tap and the heating end should have a one-way valve to prevent water
    > coming back out.
    >

    It must be one of a few that comply. Most seem to leave the filling hose
    connected. There appears to be a tap on the right of the photo , over which
    the hose iis draped. It looks as if the filling point and supply are capped
    with brass compression stop ends.

    --
    B Thumbs
    Change lycos to yahoo to reply
    Guest, Nov 19, 2005
    #7
  8. Phil Richards

    Ed Sirett Guest

    On Sat, 19 Nov 2005 11:20:28 +0000, me9 wrote:

    > On 19 Nov,
    > (Andrew Gabriel) wrote:
    >
    >
    >>
    >> The filling loop must be disconnected when not being used. This is to
    >> prevent any remote chance of the radiator water getting back into the fresh
    >> water supply. I can't see clearly in the photo, but the supply end should
    >> have a tap and the heating end should have a one-way valve to prevent water
    >> coming back out.
    >>

    > It must be one of a few that comply. Most seem to leave the filling hose
    > connected. There appears to be a tap on the right of the photo , over which
    > the hose iis draped. It looks as if the filling point and supply are capped
    > with brass compression stop ends.


    More likely 1/2" BSP brass caps.
    This year a boiler I had installed was inspected and was told that I had
    left the filling loop connected. I was sent a letter telling me to go and
    disconnect it.

    I disagree that the best practice is to disconnect the loop, but that's
    what our lords and masters require, eh. A small quantity of water
    dribbles out of the loop after disconnection (OK so you can use a cloth to
    catch it). Also a small amount of air is introduced into the system when
    it's reused. Also dust caps are not supplied with most filling
    loops so these have either to be supplied or the possibility of 'foreign'
    matter getting in has to be endured.


    --
    Ed Sirett - Property maintainer and registered gas fitter.
    The FAQ for uk.diy is at http://www.diyfaq.org.uk
    Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
    Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
    Ed Sirett, Nov 19, 2005
    #8
  9. In article <>,
    Ed Sirett <> writes:
    >
    > I disagree that the best practice is to disconnect the loop, but that's
    > what our lords and masters require, eh. A small quantity of water
    > dribbles out of the loop after disconnection (OK so you can use a cloth to
    > catch it). Also a small amount of air is introduced into the system when


    Yes. I connect up the supply end first and very loosely connect
    the heating end, turn on the water so it blows most of the air
    out of the loose connection, before tightening it up to force
    the water through to the heating system.

    > it's reused. Also dust caps are not supplied with most filling
    > loops so these have either to be supplied or the possibility of 'foreign'
    > matter getting in has to be endured.


    or of young enquiring minds thinking
    "what happens if I turn this knob?" ;-)

    Mine's in a rather shallow cupboard, and the door won't stay shut
    if the filling loop is left connected anyway.

    --
    Andrew Gabriel
    Andrew Gabriel, Nov 19, 2005
    #9
  10. On Sat, 19 Nov 2005 01:19:04 +0000, Richard Faulkner
    <> wrote:

    >Are the pipes capped and sealed? Or will the caps pop off to allow you
    >to screw the pipe on?


    From the photo, it looks like they are indeed sealed with brass,
    threaded caps.
    --s-p-o-n-i-x--, Nov 19, 2005
    #10
  11. On Sat, 19 Nov 2005 00:51:52 +0000, Phil Richards wrote:

    > Owain wrote:
    >
    >>> <http://www.philrichards1.pwp.blueyonder.co.uk/Boiler.jpg>
    >>> 2. How on earth is a system supposed to be refilled easily when radiators
    >>> are drained out? Or is there another way of allowing mains water into the
    >>> system.

    >>
    >> By connecting the flexible silver pipe between the cold water main and
    >> the radiator circuit, and turning the taps on until the pressure gauge
    >> goe up to <whatever it should be>.
    >>
    >> Are you saying there are now no screw-on connection points for the
    >> flexible pipe?
    >>> 3. How easily would it be for the engineer to get the pressure back?

    >>
    >> Very easy assuming there are screw-on connection points for the flexible
    >> pipe. I don't know what British Gas will say - be prepared for them to
    >> tell you you need a new boiler.

    >
    > Perhaps not too clear from the photo I took, there are screw on connections
    > on both pipes on the RHS. I can see now how easy the job will probably be.
    > What I don't understand is why they effectively got sealed off presumably
    > after the boiler and radiator system were installed making it difficult to
    > top it up after, say what I did, by draining out one radiator.
    >


    Because you are NOT supposed to leave the flexi pipe permamantly connected,
    although everyone actually does.
    The Natural Philosopher, Nov 21, 2005
    #11
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