Drips from flue!

[YSA]

Hi everyone, I’ve got drops coming down my flue that look a little like sap! Some black and some brownish-yellow in colour. 

 

I’ve checked the top of the boat and there don’t seem to be any holes, any idea what it might be and whether I need to do anything about it? 

 

It seems to smell a little like sulphur (not on the boat, but when I’ve scratched it off).

Edited January 20, 2023 by YSA

[Guest]

Do you mean outside?

 

Sounds like tar. Do you burn unseasoned wood?

[rusty69]

Often flues rot through first at the very top just inside the roof collar. Check in there, when it's cool. 

[YSA]

Drips are on the flue itself on the inside of the boat. 

 

Here are some pictures of the inside. I’m not sure what rotting would like like, but there are some bits that look like gaps and there’s a little bit that is falling off! 

This is the bit that’s loose/coming off

[Tony Brooks]

If you take the chimney off, how well and is in what way is the flue tube sealed to the roof collar. I would suggest that the gap should be packed with glass fibre rope and sealed on top with high temperature silicon. If you have a crack there or a gap, it is all too easy to get chimney condensation running down the outside of the flue.

 

If you have a double skinned chimney with the inner tube correctly fitted and positioned, then if it is not the flue to chimney collar seal it is likely to be as Rusty69 says. There is a chance that the roof collar is not properly sealed to the roof, but if so the liquid should only be rain water.

It looks to me as if the flue is not properly sealed to the chimney collar.

[rusty69]

23 minutes ago, YSA said:

Drips are on the flue itself on the inside of the boat. 

 

Here are some pictures of the inside. I’m not sure what rotting would like like, but there are some bits that look like gaps and there’s a little bit that is falling off! 

This is the bit that’s loose/coming off

 

That could well be your problem. Do the drips coincide with the loose bits. The loose bits could just be a build up of tar, or lifting/thinning steel. Poking it with a screwdriver will soon tell you, but if it does go through, you then have the problem of fixing it. Unfortunately, these things often happen when the weather is at its coldest.

 

Check your carbon monoxide detector is working, and in the vicinity of the stove. I think if it were me, I would want to satisfy myself of the integrity of the flue for peace of mind.

Edited January 20, 2023 by rusty69

[BEngo]

That flue needs a damn good sweep.  There appears to be a build up of about 6mm thick gunge (tar and rust) all round.  This will badly affect the draw of the chimney and increase the likelihood of making deadly CO.

 

N

 

[YSA]

I swept it recently and that didn’t budge so I thought it was part of the flue - any tips? 

[rusty69]

6 minutes ago, YSA said:

I swept it recently and that didn’t budge so I thought it was part of the flue - any tips? 

Any tips on what? Cleaning the flue pipe. I use a short length of scaffold pole. I have heard people use a length of chain. However, there is little point cleaning it if there is a hole in the top,unless it is to reduce any mess in the boat should the flue need removing. 

 

Fwiw, I clean our flue every month, which tends to block at the bottom of the flue, and pay particular attention about removing debris from the top of the back boiler (if you have one). 

Edited January 20, 2023 by rusty69

[nb Innisfree]

5 minutes ago, YSA said:

I swept it recently and that didn’t budge so I thought it was part of the flue - any tips? 

It can set like concrete, my solution was to fix a bi-metal hole saw to the end of a pole and rotate back and forth until it reaches the stove collar, only works with a straight flue of course and saw must be smaller diameter than flue by several mm to prevent jamming.

Less strenuous and almost as effective is to wait until early autumn when inside of flue is rusty and give it a good hammering (make sure flue is robust enough!) 

[PD1964]

20 minutes ago, YSA said:

I swept it recently and that didn’t budge so I thought it was part of the flue - any tips? 

I take it those photo’s are looking down from the roof collar?

 Knock the build up of crap off the collar and repack the flue/collar with fire rope, nothing permanent like fire cement, as the flue needs to move/expand when hot. The flue looks like it could be a little short, I would of liked it further up the collar and more packed.

Edited January 20, 2023 by PD1964

[Richard10002]

5 hours ago, YSA said:

Hi everyone, I’ve got drops coming down my flue that look a little like sap! Some black and some brownish-yellow in colour. 

 

I’ve checked the top of the boat and there don’t seem to be any holes, any idea what it might be and whether I need to do anything about it? 

 

It seems to smell a little like sulphur (not on the boat, but when I’ve scratched it off).

When my flue started dripping stuff inside the boat, I thought it was running from the top and down the outside.

 

After a while, it became clear that the flue had corroded, and the corrosion appeared at the top inside the boat. I suppose I'm lucky it didn't fill the boat with CO.

 

I think there have been other threads on here suggesting similar.

 

 

[magnetman]

Replace flue or take it off and put it in a decent size bonfire to burn off all the deposits then inspect it for holes. 

 

This is the sort of thing which can potentially cause a chimney fire. 

 

I've had a chimney fire on a narrow boat once. It can be quite alarming and rather noisy. It is also a bit of a risky situation in that the rapidly increasing temperature of the flue pipe can potentially be problematic for surrounding woodwork. 

 

In my case it "went mental" for about 39 seconds then stopped. I didn't actually time it but it lasted for a while.

The external terminal lost its paint during the episode. I was inside keeping an eye on things so I don't know for sure but there may have been a flame coming out the top.

 

It was loud, sort of like a rocket engine noise. 

 

 

 

Edited January 20, 2023 by magnetman

[rusty69]

Ignore the cleanliness of the flue situation at the moment. Concentrate on addressing the points Tony Brooks made, and you will likely find the cause. 

 

Then worry about cleaning the flue (unless your CO alarm is going off). 

2 minutes ago, magnetman said:

Replace flue or take it off and put it in a decent size bonfire to burn off all the deposits then inspect it for holes. 

 

This is the sort of thing which can potentially cause a chimney fire. 

 

I've had a chimney fire on a narrow boat once. It can be quite alarming and rather noisy. It is also a bit of a risky situation in that the rapidly increasing temperature of the flue pipe can potentially be problematic for surrounding woodwork. 

 

In my case it "went mental" for about 39 seconds then stopped. I didn't actually time it but it lasted for a while.

The external terminal lost its paint during the episode. I was inside keeping an eye on things so I don't know for sure but there may have been a flame coming out the top.

 

It was loud, sort of like a rocket engine noise. 

 

 

 

Wouldn't it be easier to just replace it? A straight flue pipe has a limited service life, and they aren't that expensive. 

 

A welded one may be more of an outlay, and perhaps worth fixing. 

[magnetman]

Hopefully the CO detector is one with a digital readout. I have 3 of these and they are very good. Sensitive things and it is really nice to have a warning of background CO levels rather than just an alarm to tell you bad things are happening. 

 

 

[PD1964]

11 minutes ago, rusty69 said:

Ignore the cleanliness of the flue situation at the moment. Concentrate on addressing the points Tony Brooks made, and you will likely find the cause. 

 

Then worry about cleaning the flue (unless your CO alarm is going off). 

The causes looks from the photos that the top edge of the flue is not sealed( 1st photo) flue actually looks a bit short in the collar, as Tony says this needs to be re-sealed but will need to be cleaned of build up first, as he also says the roof collar could also need resealing.

Edited January 20, 2023 by PD1964

[rusty69]

2 minutes ago, PD1964 said:

The causes looks from the photos that the top edge of the flue is not sealed( 1st photo) flue actually looks a bit short in the collar. 

It looks thin to me. There is an easy way to find out. 

[PD1964]

4 minutes ago, rusty69 said:

It looks thin to me. There is an easy way to find out. 

Yes I thought that too, but not knowing the original thickness gauge it might still be ok. Have seen some thin gauge Stainless being used on boats compared to mild steel.

Edited January 20, 2023 by PD1964

[Alan de Enfield]

53 minutes ago, rusty69 said:

Cleaning the flue pipe. I use a short length of scaffold pole. I have heard people use a length of chain. However, there is little point cleaning it if there is a hole in the top

 

Shouldn't a flue have a hole in the top (to let the smoke out ?)

[magnetman]

18 minutes ago, rusty69 said:

 

Wouldn't it be easier to just replace it? A straight flue pipe has a limited service life, and they aren't that expensive. 

 

A welded one may be more of an outlay, and perhaps worth fixing. 

 

I did say replace it in the first line of my post 

Bonfire was an alternative in case replacing it was viewed as a non viable solution. 

[rusty69]

1 minute ago, magnetman said:

 

I did say replace it in the first line of my post 

Bonfire was an alternative in case replacing it was viewed as a non viable solution. 

So you did. My humblest of grovling apologies to you. 

[magnetman]

It's okay I will let you off. 

Grovelling. 

[Tony Brooks]

Ideally the flue should poke a few mm above the roof collar and then have a double skinned chimney with the inner skin poking down into the top of the flue so any drips of condensation or rain drop into the flue rather than sit in top of the flue-collar joint. Then insulate the gap between chimney and liner with something like Rockwool loft insulation.

[rusty69]

On 20/01/2023 at 15:22, YSA said:

Hi everyone, I’ve got drops coming down my flue that look a little like sap! Some black and some brownish-yellow in colour. 

 

I’ve checked the top of the boat and there don’t seem to be any holes, any idea what it might be and whether I need to do anything about it? 

 

It seems to smell a little like sulphur (not on the boat, but when I’ve scratched it off).

Did you manage to get this sorted? 

[Tracy D'arth]

9 hours ago, rusty69 said:

Did you manage to get this sorted? 

Perhaps he is lying on the floor, overcome by the fumes?