Leaking chimney collar

[Gareth E]

Came back to the boat an hour or so ago having left it a few days. The heavy rain this morning has resulted in a leak somewhere around the chimney collar, leading to a pool of water on top of the stove and nasty black splashes on the surrounding walls.

 

As far as I can see the collar itself is well sealed, I did it last year with Sikaflex. I'd left the chimney off when I left the boat. It looks like the water may have found its way between the stove flue and the collar. This void is filled with what looks like some kind of cement (fire cement?) covered with black gunk.

 

Any suggestions for the best way forward with this?

[rusty69]

Check there is no hole in the flue between flue and collar (often where they fail).

 

If not, then

 

Dig it out and redo it,preferably with silicone(high temp silicone is available, but maybe overkill for the top of the flue, though handy at the bottom) and new fire rope if required.

[tree monkey]

As Rusty suggested it is likely to be a knacked flue, the bit between the roof liner and the boat deck is in my experience the bit that rusts through first.

This is often highlighted by leaks when it rains.

I have had mine replaced this year by a stainless bit of pipe for showing exactly this type of leak

 

 

Oh just to add, check properly, I was convinced the old mild steel pipe was fine, until I removed it for the replacement

Edited July 29, 2018 by tree monkey

[Gareth E]

Thanks there's no hole in the flue, I cleaned it out, it was all intact.

 

There's quite a gap between the flue and collar and it's not even all round. The gap is probably around an inch at its widest. Would that work, remove loose stuff, clean up and squeeze a load of high temperature silicone to fill the gap?

 

I was planning on leaving the chimney hat off. It seems to result in nasty stains down the side of the boat. I've just re painted it. Seems that using the chimney hat results in stains, not using it results in more chance of leaks into the cabin, bit of a bugger really!

[rusty69]

I've used Fire rope, various sizes available or even exhaust wrap to fill the gap in the past with plenty of goo (usually silicone) 

Edited July 29, 2018 by rusty69

[dmr]

The flue should be a sliding fit in the collar to allow for expansion. This should be "sealed" with stove rope and most people also use silicone. I just use stove rope. Either leave the chimney in place (with a coolie hat) or get a chimney cap so that this "seal" does not need to be 100% water tight. If you leave the chimney off then the rain will go down the flue into the stove.

 

It can be a little difficult to seal the collar to the roof as this does have some temperature cycling, and a lot of water can get through a very small crack.

 

...............Dave 

[Neil2]

Are you sure it's not getting in between the collar and the roof?  It's amazing how much water can get in through the tiniest gap. 

[bizzard]

I wouldn't waste yer money on special heat proof silicon, its all bloomon heat proof. Just get a cheap 2 quid tube of it, especially for up there anyway as it shouldn't get terribly hot.

[Dr Bob]

38 minutes ago, bizzard said:

I wouldn't waste yer money on special heat proof silicon, its all bloomon heat proof. Just get a cheap 2 quid tube of it, especially for up there anyway as it shouldn't get terribly hot.

I doubt if the collar/flue on our gets above 70°C so as Bizz says, any cheap silicone will do, at least for trying a repair.

[Richard10002]

I use Envirograf 1200C sealant at the stove collar, and Plumba 300C at the roof collar. I don’t think Plumba is much more expensive than normal sealant.

 

My flue was leaking, but no sign of any corrosion. However, when I took things apart to have a look, it was corroded through in parts,,and paper thin elsewhere. All hidden between the entry to the ceiling and the ceiling collar  .

[rusty69]

If there is room on top of the fire cement, you could try pouring a small amount of water on and see if it comes through on the inside.

[Gareth E]

I should add that most of the water was coming in from around the brass trim that goes round the flue where it exits the cabin, rather than running down the outside of the flue. That's why I reckon there's no hole in the flue, plus I can't see one when I shine a torch down there, neither can I feel anything untoward with my fingers. 

[rusty69]

Remove the trim and have a look next time it rains 

[tree monkey]

18 minutes ago, Gareth E said:

I should add that most of the water was coming in from around the brass trim that goes round the flue where it exits the cabin, rather than running down the outside of the flue. That's why I reckon there's no hole in the flue, plus I can't see one when I shine a torch down there, neither can I feel anything untoward with my fingers. 

Whilst debating the stainless flu replacement I gave mine a very serious talking to with a hammer and a screwdriver and came to the conclusion it was fine.

 

Being the flash bugger I am I threw caution to the wind and booked the chap to replace mine with a shiny new stainless one anyway.

 

Only on removal did it became apparent how buggered the old one was.

 

Yours might be fine of course

[roland elsdon]

Stove pipe on ours  babk cabin looked fine no leaks, but it was dropping cement dust on the range top, i dug out the cement to repack it. Screwdriver went straight through pipe. 

After removing it where it went in to the collar it went from quarter inch to tin foil in about half an inch, scary. I had recemented it only 3 years before, and  had only lit it maybe 20 times.

[Richard10002]

Sounds like it's worth removing and refitting the flue and collar. The leak will be solved if it's flue or collar related, and any flue corrosion issues will be evident if they exist.

 

Better now than leaving it until the stove is needed in October.