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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions.

Boiler dripping from pressure relief pipe



 
 
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  #1  
Old October 16th 10, 02:16 PM posted to uk.d-i-y
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Posts: 465
Default Boiler dripping from pressure relief pipe

Hi,

I have a non-condensing combi (Ariston Microgenus) from which there is
a slow but constant drip from the 15mm pipe sticking through the wall
to the outside (which I think is for emergency pressure relief?). The
pressure gauge on the boiler is at 2 bar, which is within its
tolerance range. So why is it dripping and what should I do to stop
it?

Cheers!

Martin
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  #2  
Old October 16th 10, 03:23 PM posted to uk.d-i-y
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Posts: 2,112
Default Boiler dripping from pressure relief pipe



"Martin Pentreath" wrote in message
...
Hi,

I have a non-condensing combi (Ariston Microgenus) from which there is
a slow but constant drip from the 15mm pipe sticking through the wall
to the outside (which I think is for emergency pressure relief?). The
pressure gauge on the boiler is at 2 bar, which is within its
tolerance range. So why is it dripping and what should I do to stop
it?

Cheers!

Martin


It will eventually lose pressure. In my experience, once they start leaking
they can't be cured. But, it might be worth twiddling the knob on the valve
(usually a green ridged plastic cone) which will release some pressure and
might flush debris away from the seat. They start leaking for one of three
reasons. 1, someone has twiddled the valve and let debris into the seat. 2,
the system has been overpressurised during topping up. 3, the expansion
vessel isn't functioning correctly which in turn means either the diaphragm
has gone, or it needs topping up with air: see the Wiki.
(http://wiki.diyfaq.org.uk/index.php?title=Main_Page and also
http://www.makewrite.demon.co.uk/SealedCH.html).

Replacing the valve isn't usually difficult provided you are happy to put
spanners on plumbing. Spares are cheap from BES; make sure you get the right
gender for the inlet and outlet threads. You need to depressurise the system
to do this.

  #3  
Old October 17th 10, 12:43 AM posted to uk.d-i-y
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Posts: 4,101
Default Boiler dripping from pressure relief pipe

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Martin Pentreath
saying something like:

I have a non-condensing combi (Ariston Microgenus) from which there is
a slow but constant drip from the 15mm pipe sticking through the wall
to the outside (which I think is for emergency pressure relief?). The
pressure gauge on the boiler is at 2 bar, which is within its
tolerance range. So why is it dripping and what should I do to stop
it?


If the pressure relief valve is the spring-onna-wotsit-wivva-red-cap
type, try quickly rotating the cap so it reseats. Often a bit of system
**** will clag the seat.
If that doesn't work just replace it, they're cheap enough. Dripping
from these is quite a common fault.
  #4  
Old October 17th 10, 11:12 AM posted to uk.d-i-y
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Posts: 349
Default Boiler dripping from pressure relief pipe

Grimly Curmudgeon wrote:

If the pressure relief valve is the spring-onna-wotsit-wivva-red-cap
type, try quickly rotating the cap so it reseats. Often a bit of system
**** will clag the seat.
If that doesn't work just replace it, they're cheap enough. Dripping
from these is quite a common fault.


If the relief valve is leaking, the system pressure should gradually drop.
Once a volume of water equal to that of the expansion vessel has left the
system, which at a steady drop should be a matter of hours or days, the
pressure should have gone to zero.

That the system is nevertheless still at pressure (the OP said 2 bar)
would, I suggest, seem to indicate that there is a leak in the manually
operated (and normally fully shut) mains water top-up valve.

Come to think of it, isn't 2 bar a bit on the high side? Could it be
that the relief valve is actually doing its job perfectly, and that the
real problem lies *only* with the top-up valve?

  #5  
Old October 17th 10, 11:39 AM posted to uk.d-i-y
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Posts: 465
Default Boiler dripping from pressure relief pipe

On Oct 17, 11:12*am, Ronald Raygun
wrote:
Grimly Curmudgeon wrote:
If the pressure relief valve is the spring-onna-wotsit-wivva-red-cap
type, try quickly rotating the cap so it reseats. Often a bit of system
**** will clag the seat.
If that doesn't work just replace it, they're cheap enough. Dripping
from these is quite a common fault.


If the relief valve is leaking, the system pressure should gradually drop..
Once a volume of water equal to that of the expansion vessel has left the
system, which at a steady drop should be a matter of hours or days, the
pressure should have gone to zero.

That the system is nevertheless still at pressure (the OP said 2 bar)
would, I suggest, seem to indicate that there is a leak in the manually
operated (and normally fully shut) mains water top-up valve.

Come to think of it, isn't 2 bar a bit on the high side? *Could it be
that the relief valve is actually doing its job perfectly, and that the
real problem lies *only* with the top-up valve?


Thanks to all. I think Ronald could have hit the nail on the head. The
system has been dripping for weeks without being topped up, but is
still at full pressure, so I guess is must be the top-up valve.letting
through. I shall make further investigations ...
  #6  
Old October 17th 10, 12:32 PM posted to uk.d-i-y
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Posts: 6,024
Default Boiler dripping from pressure relief pipe

Martin Pentreath wrote:

So why is it dripping


More to the point does boiler dripping taste as good as beef dripping?
 




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