Leaky flue, apparently very bad job done - what to watch out for?

[lili_z]

3 years ago after buying a flat, before moving in, I had my boiler replaced - I live in a flat, the boiler room is quite far from external wall (approx. 6-7m) and therefore the whole operation was rather tricky - the flue needed to go through 3 internal walls and is boxed just under the ceiling. I thought it was worth doing though, as the old boilers in these apartments were notoriously bad (PowerMax) and I hoped I'd have a peace of mind for years to come. I lived through "no hot water/no heating for 3-4 weeks" twice before, when PowerMax died in my rented apartments and really didn't want to risk it.

Unfortunately 2 days ago I had the annual check and the British Gas engineer found a water leak from the flue (near the boiler), he shut it down as safety hazard (so no hot water or heating for the third time, lucky me!) and basically left me with not much more comment. I managed to get some engineers in to see if they can fix it, and overall message is that the guy who originally fitted in has done an absolutely dreadful job. I'm quite surprised that none of this has been raised by the British Gas engineer on the annual check last year but... that's another issue.
The installer hasn't kept the manufacturer's standard (it's a GlowWorm ultracom boiler) when it comes to the required drop of the flue - it's meant to be 44mm per m yet it is only about 12-13cm across approx. 6-7m flue, plus some extra bends on the way that I wasn't even aware of as they're in boxing. He hasn't mounted the flue in brackets. He hasn't even properly screwed the flue parts on the joints. It turns out the flue leaked in numerous places - vast majority very tiny leaks, probably only occasionally as it's simply some spots in the boxing that I now noticed. It made it through the boxing only once - he came back at that time and "fixed" it. Overall, I have reported him to Gas Safe and hoping they can come and inspect it - although not sure if it's too late for this now.

In any case, could you please comment on the whole "drop" aspect and how critical it is? Out of three engineers that came 1 seemed extremely concerned about keeping to this requirement to the letter, and it turns out that in my flat it's going to be extremely difficult if not impossible to get such a huge drop. Would this be the major factor that makes it leaky, or would it be more due to the other factors - the extra bends, not sealing it, not mounting it properly? I'm really worried I will get another "hacker" who will only care about making it appear to work, and within next 2-3 years I'll have to go through this whole nightmare again.

When it comes to this required drop, does it have to be placed on an angle throughout the whole length (so literally 2.5degrees straight line), or can it be, say, 1.5deg angle, then a sharper drop through a bend, and again 1.5deg angle (as long as from one end to the other the average is 44mm/m)? I simply cannot see how, with the walls and appliances etc. on the way, could this 44mm/m drop be achieved through 2.5deg drop...

How can I tell which engineer to trust? What should I ask / watch out for / should I be truly concerned about not reaching this drop or would it be enough if somebody increased it just slightly, and the real problem was how badly the flue was assembled and mounted?

Any advise greatly appreciated.

 

[simond]

This raises all sorts of issues, clearly both the installation and subsequent inspections have all been negligent.

In this respect your installer is no worse than your service maintainer.

It is also worth mentioning that Vaillant Group products have issues with the seals used to make a watertight seal between the flue sections; ask to look at some in the elbows, chances are they are all shrivelled and wrinkled.

Welcome to our industry and remember, we have the same proportion of bad apples as decorators and electricians. Gas Safe Registration involves a multiple choice exam with open books, chancers can and do get through.

 

[simond]

To answer you question, the only compliant solution is by meeting the manufacturer stipulations, and gas safe technical bulletin 088.

In other words the flue drop given in the instructions, anyone that says otherwise is a chancer. The fact that you would need to limbo under it is no concern of the manufacturer and is not a mitigation to the installer to break the rules.

 

[muggles]

As simond has said, the only way the boiler will be correctly installed, and therefore compliant with regulations, is if it is fitted to the manufacturers' instructions. MI's are the law of the land when it comes to boiler installation, and not even Gas Safe or British Standards have the power to override them, certainly not installers. These clearly stipulate a fall of 44mm per metre for your boiler. Go for the engineer who insisted that the rules be followed to the letter, he's clearly got his head screwed on properly on this aspect at least. Getting recommendations from neighbours is also a good way of finding good engineers, as is www.buywithconfidence.gov.uk, which is run by Trading Standards although it's not available in all areas of the country

The flue is concentric - it's a pipe inside a pipe. Air is drawn in through the outer pipe and the inner pipe is the exhaust. If water is in the outer pipe, then it's either rainwater getting in from outside (problematic as it could cause corrosion, but not immediately life-threatening), or the exhaust pipe is leaking into the air intake pipe, which is very definitely life-threatening


You say there are bends in the flue run. How many bends, and are they 90º bends or 45º bends? With your flue run, you're allowed a maximum of three 90º bends, or six 45º bends, or one 90º bend & four 45º bends, or two 90º bends & two 45º bends. Any more than that and I'm afraid that you have further problems, as the maximum length of flue for your boiler has been exceeded and either the number of bends needs to be reduced, or the boiler needs to be relocated closer to the flue terminal.

 

[lili_z]

Thanks for the explanation re: the pipe within a pipe. I think it's more likely that the water is coming from the outside since that bad leak for which we had to call the original engineer was during very heavy winds and rain, and it was on the joint closest to the external wall. Overall, we're getting some nasty wind tunnels, particularly since another apartment block was build opposite of ours, so it's not unlikely that it blows some water in.

As for the bends, I am not 100% sure how to count it. Overall, the direction of the flue is simple - up from the boiler, to the right all the way to the outside wall. However, within this roughly straight line there are some tiny bends, like zig-zags. It comes up from the boiler, 90deg bend to put it (almost) horizontally (does this 90 count?), then it makes a tiny zig-zag so basically the flue is positioned still in the same direction, just slightly away from the wall, parallel to where it came out of the boiler, then a bit further down it has a triple tiny zig-zag (going back towards the wall and tiny bit up...), and then it continues straight all the way out. I was completely unaware of these zigzags until the second and third engineers who came noted them. I think the reason for the some of them it is that after coming out from the boiler room, before it reaches the bathroom, it goes through a "shaft" with various pipes and there is a massive pipe going from the floors above to floors below right next to wall (global water supply? waste? No idea what runs in it). So to avoid it, he took the flue away from the wall and then back towards the wall... I'm not sure why he did an up-zigzag as well (rather than just running the pipe on an angle). If I count the actual "bend parts" I think it's 3 of them - 1 for the "move away from the wall" next to boiler, and 2 for the zig-zag in the bathroom. I think all of them are 45deg.

I find it quite hard to describe, tried to put up a diagram, not to scale , green lines are walls between rooms. Not sure if it helps, I'm not particularly talented in arts.

I am also learning much more about boilers and flues than I ever wanted to know...

 

[ollski]

This raises all sorts of issues, clearly both the installation and subsequent inspections have all been negligent.

In this respect your installer is no worse than your service maintainer.

Flue in void with no inspection hatches and no signs of a leak?, not sure how that would leave a maintainer negligent?

 

[lili_z]

Flue in void with no inspection hatches and no signs of a leak?, not sure how that would leave a maintainer negligent?

Just to clarify, there ARE inspection hatches around every flue connection, and the whole installation right now is as accessible now as it was during previous inspection (boxing wasn't taken off or anything). Everything that has been discovered now could have (should have?) been detected during the previous annual boiler check. I am an ignorant, I was unaware of the bends, leaks etc. - but the guy who visited my apartment a year ago shouldn't have been. That's his job. He just didn't take the time to look in details into how the flue is laid, to verify its angle or any of these things.

 

[simond]

The maintainer is negligent. If you service the boiler, you inspect the flue, you open the hatches etc. If it is not installed correctly you write it down and advise the customer, how you advise them depends on the severity of the defect.

I thought we all did the same course?

 

[Agile]

If you side view is correct then there is sufficient height to obtain the maker's recommended flue slope.

The slope is solely to enable water inside to run back to the boiler. They select a slope which is reasonable for the purpose. That has to be a uniform slope all the way.

It will however still work fine if it was half that as long as it was uniform. One of the things a maker will take into account is how accurately an installer is likely to set the flue. But the situation is that an installer is meant to install according to how the maker says it must be done. How closely they bother often is related to how much they are charging for the job. Cheaper then often less carefully!

Rainwater entering at the terminal into the outer ( intake ) part is sometimes a problem during adverse weather conditions or severe local winds caused by other buildings etc. Not very well protected on most flues either.

Tony

 

[simond]

I don't think you are qualified to offer the advice that it will work fine with half the slope, Tony. We all know that it will work, but how long will the flue seals last? How is the gas bouyancy, and thus max flue length affected?

Without a test lab you don't know the answer, and as far as I know you don't work for Vaillant Group in R&D. (But if you did, I'd have a long list of suggestions!)