Boiler Losing Pressure - I can see dripping from a valve

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Hi,

I have a Worcester Greenstar 30CDi boiler long with a separate hot water tank. I have noticed in recent weeks that the pressure is dropping to zero almost daily after the CH has been running. It doesn't appear to drop when just the HW schedule is on to heat the water tank.

I can see there is an open plastic connector between 2 of the copper pipes that has water dripping when the CH is on. This leads outside to be dumped so it seems this is why its dropping. I do not know why though. I have added a couple of links to a picture as I cannot see any label on the connector to confirm what it is (hopefully the experts will know!)

https://app.box.com/s/n2rc7rdx8gllkg4quvz3y1erdpleexy0

https://app.box.com/s/epsz54nfi2wjw8li5p9ig0o4miz0gkot

There is an expansion tank above this pipework which may be playing a part. The whole system is around 10 years old, maintained annually and still appears to be in good condition aside from the pressure issue.

Any advice appreciated so I know if its something I can fix as a competent DIY'er or I need professional help.

Thanks
 

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CBW

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Sounds like you have an expansion related issue, but quite possibly need a G3 registered engineer on account of your unvented cylinder.
 
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what does the pressure guage on the boiler go up to when the heating has been on for an hour ?
 
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1. The "open plastic connector" is a tun dish. Its purpose is to provide visible evidence of water flowing, particularly when it should not be. It is part of your unvented hot water system, and not part of your central heating system.
2. You appear to have an issue with the unvented system. As CBW says, this may need a G3 registered person. These cylinders require an annual service for safety reasons.
3. The expansion tank is for your unvented cylinder, not for the boiler.
4. If the boiler pressure is dropping after running the central heating, this is likely to be caused, as CBW has stated, by an issue with the boiler's expansion vessel. If your boiler is a system boiler or a combi boiler (unlikely) then the expansion vessel will be inside it. If it is a heat only / regular boiler, look for an external red expansion vessel.
5. I'd suggest you get someone in who is both Gas Safe and G3 registered and have the issues addressed. It is unwise, and arguably illegal, for anyone not qualified and currently certified to work on either appliance.
 
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what does the pressure guage on the boiler go up to when the heating has been on for an hour ?
It has been running for an hour now and it was up to 2.75 Bar approx. I normally have it just over 1 bar when cold. It was not dripping with water when I looked so it doesn't appear to be happening at "peak pressure" if that helps.

** EDIT - based on oldbuffer's reply, it would appear its not related to the CH. I will test and confirm as the basic observations so far was that it wasn't going down when the HW was on (its on twice daily for 30-45 mins) but only when CH on but that may well not be the case.
 
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It has been running for an hour now and it was up to 2.75 Bar approx. I normally have it just over 1 bar when cold. It was not dripping with water when I looked so it doesn't appear to be happening at "peak pressure" if that helps.
you have an expansion vessel problem with the boiler, this is causing the pressure drop, the water drips in the Tundish are from the DHW cylinder and nothing to do with the system pressure loss, most likely that both expansion vessels just need charging, supposed to be checked every year but hardly ever done
 
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1. The "open plastic connector" is a tun dish. Its purpose is to provide visible evidence of water flowing, particularly when it should not be. It is part of your unvented hot water system, and not part of your central heating system.
2. You appear to have an issue with the unvented system. As CBW says, this may need a G3 registered person. These cylinders require an annual service for safety reasons.
3. The expansion tank is for your unvented cylinder, not for the boiler.
4. If the boiler pressure is dropping after running the central heating, this is likely to be caused, as CBW has stated, by an issue with the boiler's expansion vessel. If your boiler is a system boiler or a combi boiler (unlikely) then the expansion vessel will be inside it. If it is a heat only / regular boiler, look for an external red expansion vessel.
5. I'd suggest you get someone in who is both Gas Safe and G3 registered and have the issues addressed. It is unwise, and arguably illegal, for anyone not qualified and currently certified to work on either appliance.

Thanks oldbuffer - if this is not something I can safely look at myself, that's all I need to know and wont be messing around with it. I have a British Gas service agreement which will cost me £100 or so for the callout. I dont think they (or any of the other companies who have maintained it over the years) have ever looked at the expansion tank, just the boiler itself.

I was hoping it would be a case of making a minor adjustment to relieve trapped pressure in the tank but as you say, I will leave it with the experts and keep topping up manually in the interim.

Thanks to everyone who has contributed
 
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you have an expansion vessel problem with the boiler, this is causing the pressure drop, the water drips in the Tundish are from the DHW cylinder and nothing to do with the system pressure loss, most likely that both expansion vessels just need charging, supposed to be checked every year but hardly ever done

Yes, as per my latest update I dont recall anyone ever checking this over the years (just the boiler) despite using various big name energy providers and local trades too!
 
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Yes, as per my latest update I dont recall anyone ever checking this over the years (just the boiler) despite using various big name energy providers and local trades too!
very common, I done two last week and lad was asking why I was doing that as no one else has to, you will need a G£ engineer to do the unvented one, he will probably be able to do the boiler one too, not a big job when you know what you are doing
 
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Thanks Ianmcd. As a side issue, I have also noticed very recently that when the heating stops, there is a bang. Pretty loud, like its coming from the inside of the boiler - like a single hammer strike to the metal casing. Is it possible this is related to the pressure issue? As the boiler is in the loft space, its not every day I am near enough to hear the bang but it did happen just now when the heating went off after an hour and would seem to coincide with the pressure drops.
 
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Thanks Ianmcd. As a side issue, I have also noticed very recently that when the heating stops, there is a bang. Pretty loud, like its coming from the inside of the boiler - like a single hammer strike to the metal casing. Is it possible this is related to the pressure issue? As the boiler is in the loft space, its not every day I am near enough to hear the bang but it did happen just now when the heating went off after an hour and would seem to coincide with the pressure drops.
yes could be the pressure releif valve closing, get both vessels properly charged and see if the pressure increase and the noise stops
 
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Just a short update on this - I have had the heating on a couple of times today (no hot water) and have had to top the boiler up on both occasions, with it dropping to zero bar.

Not sure if that makes any difference to the comments above.

I have raised a case with B.Gas who are coming out for the £99 excess fee on the 17th November but hopefully I can get it resolved sooner with a local guy I have used successfully in the past (I am checking he is G3 registered).
 
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I would be telling BG they are doing it free as they never carried out a proper service of the boiler, personally I wouldnt charge that for doing both expansion vessels
 
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Short update on this following the BG visit yesterday. Both my internal expansion tank (in the boiler) and the external larger tank were fixed yesterday. I was surprised to see the tanks were pressurised using a basic foot pump!

I was told both tanks were completely empty of air, therefore full of water so no expansion was possible.

I asked if this should be checked as part of the annual maintenance but was told it wouldn't usually be checked. To be fair, I have had local independents service it for the most part, along with multinational maintenance companies (homeserve) and other national household providers and I dont recall anyone ever looking at it (the internal one may have been checked but I have never heard of this being mentioned and I am inquisitive when I have this kind of work done and ask about it, everything OK, the usual stuff). I will now make sure they do.

However, when the heating goes off I still get the very loud single bang. It may be irrelevant but the heating goes off, then I hear the motorised valve turning, then the bang. Is this still relating to the expansion tank as I am going to be calling BG out again to rectify it given its not resolved?

It is very loud and concerning. I have tested with the heating on for 15 minutes as well as an hour or more and the bang is the same.

Of note, the pressure now seems stable and isn't dropping so that's a big step in the right direction!
 
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CBW

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Motorised valve could be fitted the wrong way?
 
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