Boiler Flue Issue
Posted: May 7th, 2019, 7:02 pm
I have a Worcester-Bosch Highflow 440 combi boiler. I started noticing a few years ago that on the terminator that sticks out of the wall the plastic tube coming out of the very end was starting to disappear. The picture in this post that I found when googling for all things flue-related could almost be a photo of my flue as it was when I started noticing the issue a few years ago, it shows perfectly what I have...
https://www.pistonheads.com/gassing/top ... &t=1241107
Recently the whole of the final plastic projection has disappeared apart from a little sliver of plastic at the bottom. At first I thought it was melting but it is interesting to see the guy on the post linked to above say that his "seems to have shattered in the frost". That would seem to make sense since one would assume the flue is engineered for heat. Also, we've had scaffolding up recently on the wall where my flue comes out and I wonder whether the scaffolders putting up the scaffolding or the workmen subsequently working on it might have broken off the final bit. I've been away for a few months so wasn't there to see what was going on.
The scaffolding has given me the opportunity to go out and have a look after the builders pack up for the day and the final bit of plastic at the bottom is very crumbly, I easily broke a bit off with my fingers. Also, with the boiler running none of the flue feels particularly hot (it is a condensing boiler after all which I believe means that it extracts heat from the flue gas as best it can) so I doubt it was ever a heat/melting problem and maybe was a frost issue. I am away in the winters and don't have the boiler running so the flue would have been cold.
Anyway, I'm now left with what to do and that's becoming a nightmare. One company that I got round to look at it said that they couldn't replace it because if they did then new work would need to comply with latest standards and the flue comes out into a big approx (5m x 5m) light well and exits about 2.7m below roof level whereas latest regs apparently say it should be no more than 1.1m below the top of the light well. There's all sorts of other stuff in the way, both on the inner and outer walls, so it's going to be a nightmare to fix. The obvious solution of fitting a plume management kit isn't an option because one isn't available for my flue.
I'm now wondering exactly what purpose that final bit of plastic tube fulfils and whether one option might be to do nothing. Some posts from plumbers on one plumbing forum (for which I now lost the link) suggested that in theory it reduced the risk of any carbon monoxide getting back into the air intake but was one of those things where everything would probably be just fine although if a plumber sees it it is an item they are supposed to flag and shut off the boiler.
Since fixing this is looking like it will cost me over a thousand pounds, possibly well over since the scaffolding is coming down next week and if I cant get an engineer in the next few days I would have to re-scaffold at my own cost, I'm actually wondering whether neatly cutting off the final bit of plastic tube at the bottom while I still have scaffold access and hoping no one picks it up (i.e. pretty much do nothing) might be one option. Other flues in my light well seem to have no plastic tube projecting, in fact they look very much like mine would look like if I were to do the above.
One other slightly more ambitious option that occurs to me is to get a length of 85mm diameter metal tube which I could fit to the outside of that little metal lip just before the plastic tube becomes visible to keep a bigger separation between where the flue gasses come out and where the air intakes are. I think that would be pretty simple to do and I've found a suitable pipe for £15 which is a heck of a lot cheaper than the £1,500 it looks like it would cost me to get it officially fixed which essentially involves reworking the entire flue.
Any thoughts, comments, other suggestions?
- Julian
https://www.pistonheads.com/gassing/top ... &t=1241107
Recently the whole of the final plastic projection has disappeared apart from a little sliver of plastic at the bottom. At first I thought it was melting but it is interesting to see the guy on the post linked to above say that his "seems to have shattered in the frost". That would seem to make sense since one would assume the flue is engineered for heat. Also, we've had scaffolding up recently on the wall where my flue comes out and I wonder whether the scaffolders putting up the scaffolding or the workmen subsequently working on it might have broken off the final bit. I've been away for a few months so wasn't there to see what was going on.
The scaffolding has given me the opportunity to go out and have a look after the builders pack up for the day and the final bit of plastic at the bottom is very crumbly, I easily broke a bit off with my fingers. Also, with the boiler running none of the flue feels particularly hot (it is a condensing boiler after all which I believe means that it extracts heat from the flue gas as best it can) so I doubt it was ever a heat/melting problem and maybe was a frost issue. I am away in the winters and don't have the boiler running so the flue would have been cold.
Anyway, I'm now left with what to do and that's becoming a nightmare. One company that I got round to look at it said that they couldn't replace it because if they did then new work would need to comply with latest standards and the flue comes out into a big approx (5m x 5m) light well and exits about 2.7m below roof level whereas latest regs apparently say it should be no more than 1.1m below the top of the light well. There's all sorts of other stuff in the way, both on the inner and outer walls, so it's going to be a nightmare to fix. The obvious solution of fitting a plume management kit isn't an option because one isn't available for my flue.
I'm now wondering exactly what purpose that final bit of plastic tube fulfils and whether one option might be to do nothing. Some posts from plumbers on one plumbing forum (for which I now lost the link) suggested that in theory it reduced the risk of any carbon monoxide getting back into the air intake but was one of those things where everything would probably be just fine although if a plumber sees it it is an item they are supposed to flag and shut off the boiler.
Since fixing this is looking like it will cost me over a thousand pounds, possibly well over since the scaffolding is coming down next week and if I cant get an engineer in the next few days I would have to re-scaffold at my own cost, I'm actually wondering whether neatly cutting off the final bit of plastic tube at the bottom while I still have scaffold access and hoping no one picks it up (i.e. pretty much do nothing) might be one option. Other flues in my light well seem to have no plastic tube projecting, in fact they look very much like mine would look like if I were to do the above.
One other slightly more ambitious option that occurs to me is to get a length of 85mm diameter metal tube which I could fit to the outside of that little metal lip just before the plastic tube becomes visible to keep a bigger separation between where the flue gasses come out and where the air intakes are. I think that would be pretty simple to do and I've found a suitable pipe for £15 which is a heck of a lot cheaper than the £1,500 it looks like it would cost me to get it officially fixed which essentially involves reworking the entire flue.
Any thoughts, comments, other suggestions?
- Julian