Convesa twin wall flue

[JT19]

Hi guys I've got a convesa twin wall flue running internally in my cottage. I fitted it about 4 years ago and it's great. 

It was a tad low to the ridge so I decided to extend it by 500mm. I used a convesa structural band rather than the standard connecting band. 

It started to let water in in-between the two walls. So I lowered it back down. 

Tomorrow I plan on refitting it but with some heat proof sealant which is good to 300°c. 

 

My question is how hot does the top of a twin wall flue  get?  

 

Regards  

Josh 

 

 

 

 

[slim reaper]

Its not recommended to seal some  flues, its in the instructions not to  . By sealing between the new and old may hold more water in that could have run out of the joint . What cowl do you have

Edited January 22, 2021 by slim reaper

[PhillH]

Hi @JT19 I have a similar issue but can not trace where the water is coming in. Do you know where water is getting in between your two walls?

[JT19]

I have a wind cowl fitted. It's not the cowl that's leaking. I thought it was at first before I went up to investigate. 

Water is getting in via the structural band. It's then getting into the cavity of the flue pipe where the insulation is. It was all wet and was dripping out of the flue inside the airing cupboard where the pipe is. 

I plan on putting some sealant in the structural band so water doesn't get in. Just wondered what temperature the pipe got up there about 4 meters from the stove. (It's a small cottage with low ceilings). I'm thinking it would be well below 300°c but thought I'd check here to be sure...

[JT19]

Just now, PhillH said:

Hi @JT19 I have a similar issue but can not trace where the water is coming in. Do you know where water is getting in between your two walls?

I'll get pics up tomorrow as it'll explain it easier. 

Do you have a convesa flue pipe? 

[slim reaper]

 Can you swap the bands over ,move the structural band inside . the temperature on the outer skin is way below 300 Id be surprised if it even went over 100. The temp on my twinwall hardly gets above 50-60 6” above the single skin

Edited January 22, 2021 by slim reaper

[PhillH]

I'll get pics up tomorrow as it'll explain it easier. 
Do you have a convesa flue pipe? 

No, I’m not sure on the make as it was already installed but it is annoying the life out of me trying to find where the water is getting in. Would not mind but it was like a tap with the heavy rain we have had. Interested to know your findings.

[JT19]

I was thinking about doing that and have the band inside but it would be a faff and after measuring up the band would be poking through the roof. 

I could use the non structural band I guess but prefer the idea of it as i have the fear of it blowing off in the wind 🤣

[slim reaper]

So you only have two locking bands on the whole flue?

 

If the locking band would be Part below and part above the roof it doesnt sound like the layout was very well designed...was it a signed off install?

If you look at the video I posted in a recent thread, thats a Convesa h cowl with a standard locking band. were above 700ft in the teeth of the prevailing wind and it hasnt blown off in 5 years

 

Edited January 22, 2021 by slim reaper

[Mull]

 
My question is how hot does the top of a twin wall flue  get?  
 
Regards  
Josh 
 

Not very hot I’d imagine, it’ll get pretty warm at any bends, above roof level it will be luke warm at best I’d think.
It’s maybe getting more rain since you raised it?