[Closed] Woodburner - water dripping down flue

Yup, get him back, did you have a cowl fitted? not essential to be compliant, but a sensible option.
Black water indicates the wood you are burning contains too much moisture or you are just not getting the stove up to its correct operating temperature.

Yes, got a cowl and a new chimney pot fitted as the existing one was a low level one. I'm quite careful about the temperature and use a flue thermometer to ensure it's right.

We had this, but we hadn't had it installed. Previous owners had.

When we inspected the pot, it was almost like a bird bath, so when it filled with water, it ran down the sides and some of it when down the liner.

What cowl have you got on? Can you see from outside?

This one:

BIL had one of the those and the same problem. The top part doesn't overhang much so with a bit of wind the water dripping off goes down the flue. Bigger cowl with more of an overhang sorted it.

I prefer to put the thermometer on the actual stove and not the flue as it can otherwise give a rather misleading reading, especially when first lit.

Also I've found that our thermometer (and I'm sure they're all very similar) reads about 30c higher than the actual temperature.

Do you regulate the temperature of the burn? What a faff if so. Couldn't be arsed with that, just light it and get it glowing.

They are not super accurate, one of mine under reads by about 30C. They is assuming my ir thermometer is more accurate...a wild assumption perhaps.

Anyway, even when burning very nicely you will get a little bit of soot over time, not much, but a little. It probably doesn't take much soot to turn rain water black.

Do you regulate the temperature of the burn?

I like to know where it's at. I try to keep the stove at 200-240c.

Is there a liner fitted? Something isn’t right. I would as your fitter to come back and fit a better cowl with bigger top hat style to shed water

Update.

Had the fitter back who's fitted a different cowl which has an extra flat later that should shed the water better. Needless to say, it doesn't and rain is still coming in. I also asked him to replace the fire rope around the top of the flue as it had gone black with all the water soaking through it and smelt like 1000 concentrated cigarettes, he applied silicone followed by the fire rope.

We've had the fire on for the first time tonight and about an hour in I heard a sizzling noise and water began weeping through the fire rope. I think something is fundamentally wrong with the install and I've lost confidence in the fitter's ability/desire to solve the problem. The diagram below shows the setup:

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This seems wrong to me. There is always going to be a void where water/soot can gather due to the difference in size between the flue and the clay liner.

Are there any experts here who can offer some advice?

I think that is a common way of doing it but I prefer a full flue liner.

Its not the register plate etc that it the issue - its the water getting in thats the issue

It will probably be condensation, is it dry wood your burning? That's why its doing it when your burner is lit. Have it roaring, it will get worse before it gets better.
Would be better with a liner even though it's got a clay liner.
If you don't want a liner you can mortar round the flue to create a sort of funnel into the flue so any water would be going into the burner, you'll also get better draw

It will probably be condensation, is it dry wood your burning? That’s why its doing it when your burner is lit. Have it roaring, it will get worse before it gets better.

Yes, dry wood.

We have a wood stove in a very cold part of the house. It used to leak water as described, and also was a pig to light - flew was just perma cold I think.

Took many visits by installers (mostly FOC) and solutions were as follows:
more of a cowl (the whirly variety) and also a flue liner (the concertina variety) with the cladding between old stone flue and pipe. I assume allows a better seal all round.

Since then - next to no water.

Forget the cowl, it'll be condensation.
I've seen it plenty, even with kiln dried fuel.
Burn it hotter, or accept that you need a liner to funnel the condensate back down inside the stove.
This is why I don't connect to clay, and deffo don't poke a pipe through a reg plate into a void.
Sealing against determined slumbering and tar production is all but impossible.
Ironically, some of the newest cleanburn stoves are potentially worse than old school stoves.
An interesting read Mr Soot

you can get top hat style connectors to join stove pipe to register plate/wider flue

https://www.stovefitterswarehouse.co.uk/collections/bits-n-bobs/products/sump-adaptor

Here's one I looked at last week. 9" liner, about 1.5M down you could maybe just get a fist through it. Nasty hard glassy tar, will likely need Creaway treatment then flailing.

Ancient, huge stove. Pipe into register and a huge void. Constantly slumbered. This is where it leads...

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Thanks neilnevill, that sump adapter makes a lot of sense, essentially catching anything coming from the 6” clay liner. Not sure how it’s suppose to attach to the register plate??? Presume the spigot is male so would go inside the vitreous pipe?

For the he record, I always keep an eye on temperature and the run the stove around 250 Celsius, never letting it slumber.

[i]Forget the cowl, it’ll be condensation.
I’ve seen it plenty, even with kiln dried fuel.[/i]

I burn seasoned but not kiln dried. My flue goes through the register plate and then opens to normal chimney. I think I have drops of water come down the flue once in five years and that was after a huge storm, my cowl is similar to the picture earlier. I've never had condensation dripping down. When I used a mirror to check the top of the register plate it just looked dirty with a few bits of debris on it, no sign of water having dripped or pooled on it.

Can't see why the Mattrgees issue would be condensation when it only leaks during heavy rain. PS My install is similar to your image (mine opens up above the register plate and then reduces back to the concrete liner) I believe this is correct (although some will say you absolutely must use a full liner)

Mattrgee, not quite sure but I think so. Try contacting stove fit fitter manual for advice?

My stove is flexible lined up the flue but mum's is like yours. Her flue is larger I think too, and has an open pot up top. In ~20 years they had a tiny bit of water dribble down the wall behind the stove just once or twice and I swept the flue just a few weeks ago so I know it had just a little dry soot in it. However, it's fully internal in the house, if yours is on an outside wall it will be cooler and that can be the problem.

Did he do a pressure test first?
If it was my house I would drop a liner down, 125mm if it's too tight for 150mm and fit an appropriate stove for the smaller liner.

Contact HETAS they will come out and inspect the installation.

clay liner here with a top hat funnel at the bottom into flue pipe.

No cowl at all up top.

No water at bottom.

My mate did his like yours on stove fitters advice and ended up with black sooty water all over his polished slate hearth every time it rained and the fire wasnt on..... after about 6 attempts they found a cowl that stopped the rain.

I've used this cowl in exposed locations to stop rain blowing in.
It's proved very effective.

https://eurocowl.co.uk/shop/?swoof=1&product_cat=rain

Did he do a pressure test first?

Nope.

I’ve used this cowl in exposed locations to stop rain blowing in.
It’s proved very effective.

https://eurocowl.co.uk/shop/?swoof=1&product_cat=rain/blockquote >

Thanks, which one of those cowls did you use?

 

Sorry - the mini Eurocowl is the one.
I use something similar to the Topguard 2 most of the time, but the Eurocowl is the one I use any time a ferry is required to get to work 🙂

The first stove we had fitted was into a clay lined flue. Our [trusted] fitter refused to fit a clay flue adapter as he said he'd seen too many were black oily water was coming back down into the stove.
He would only fit a flexible liner into the existing clay liner - which is what we did.

The first stove we had fitted was into a clay lined flue. Our [trusted] fitter refused to fit a clay flue adapter as he said he’d seen too many were black oily water was coming back down into the stove.
He would only fit a flexible liner into the existing clay liner – which is what we did.

How wide was the clay liner out of interest? Ours is only 6", not sure we'd get a liner down it.

It's not the cowl.

It's not the flue.

It's because you are burning larch, which even when fully seasoned produces a horrible wet stinky tar, which dribbles down, bubbles around the register plate and drips down behind the stove stinking the room out with acrid smoke. You can prevent it by getting the stove roaring hot very soon so as to heat the flue properly from bottom to top but in the end the only answer is to throw away the larch and get some nice bright clean-burning birch.

Is it larch?

Number 1, The Larch?

We get the odd drip during prolonged rain on one of ours, but it is into the stove. Never thought much of it, just assumed it was down to weather conditions forcing some moisture into the flue. The other stove at t'other side of house doesn't have any problem with drips. Both have those standard bird cage type cowls on top.

am i the only one that thinks its a bit odd to ask if its larch after proclaiming the larch he is burning is his problem ?

I'm not burning larch.

So maybe you're closing the air down too soon before the flue has warmed thoroughly and you're getting condensation along with the rain that's dripping down? Rain would be wetting the clay liner and making it cold, meaning condensation is far more likely.

And I'll dig my orthopaedic shoes out if someone can provide evidence that larch is bad, otherwise I'll put that with the 'stove wives tales' like pine causes chimney fires. It's rubbish. Dry the wood properly, it then burns nice and hot and nice and clean.

Op, is your chimney on an exterior wall? That will make it cooler.

Op, is your chimney on an exterior wall? That will make it cooler.

No, internal wall, centre of the house.

I'd be willing to take issue on the larch! We have been using wood burners for over 25 years in two different houses and have never suffered the way we did when we started on a load of larch; suddenly we had stinking brown water dribbling down the flue and down the wall, sizzling on the hot bits and filling the room with smoke. It was an unpleasant experience and we only managed to get rid of the larch by waiting until later in the evening when the flue was thoroughly hot then burning the stuff on full open vents to keep the fumes moving up the flue. Never again.

i burn anything that was once a tree and is free or cheap.

I've had all sorts of wood through my stove.

The main key take away I've found is never bring it home and burn it - regardless of source even if i have paid good money for it , its never as dry as claimed.

IF i have to buy wood i buy it at least a burning season before i actually need it - but i now know how much i get through in a season.

If he didn't do a pressure test how would he know it wouldn't leak carbon monoxide into living areas?

globati, you said 'a load' as in delivered? was it dry? the eternal question. Wood is all the same really, its cellulose, lignin and water. the amount of water in the green tree varies and the cell structure and lignin content can affect how fast it dries, but once dry the only variation then really is cellulose to lignin content slightly. A more resiny wood (more lignin) will actually burn a bit hotter, so long as its given the air and there's nothing there that should make tar, any more than any other wood that isn't burnt hot. Some wood types are hard to dry though, oak because of its cell structure takes ages, birch and some other have such a resinous waterproof bark they can trap the water in and rot, but once this is overcome and the wood is properly dry, it should burn like any other. that said....AFAIK I've never had Larch so I don't know what its like to dry...or burn.

I'm very much enjoying some silver birch currently, mixed with oak.

I thinned out a woodland at a mates school last winter and got a load of larch last winter from it.

It's been drying out all summer.

I dug out some tonight and threw it on the fire.

We are not drowning in tar yet.

A couple weeks ago I picked up a trailer load of freshly felled pine. It's currently oozing sap out all over the slabs at the back door. Needless to say it won't be going near the fire this year.

Larch aside, any suggestions on how best to resolve this?

In a standard install with a flexi liner, the liner would be continuous from the chimney pot to the stove flue, thus no where for deposits to collect other than in the stove itself. The setup I've got is essentially an open joint that is allowing soot, rain and condensation to collect and escape.

Surely it would be better for the clay liner to attach directly to the flue? Obviously it's 6" compared to 5" but it would create a more typical install.

Long term, maybe get a different outfit to put one of those sump adaptors in?

this sort of thing

That way anything coming down the chimney is only ever going into the stove. It's probably a mornings work for a pro. I now defer to the pros on the forum.

Let's face it, £39 for the sump adapter and a bit for fitting, isn't much to waste if it doesn't work, and although I reckon steel liners are best, I'm sure that sump adapter will work.

What ever solution you choose though (do nothing, adapter, full liner) you ought to think about more heat in the flue. Personally I like to let the stove rip threw the first load to warm the flue, and last load to really shift any water. That's on top of seasoning all my wood myself for 12-24 months.

I'd get a chimney sweep to look at it. They might be able to tell you what's going on and how to sort it.

In a standard install with a flexi liner, the liner would be continuous from the chimney pot to the stove flue, thus no where for deposits to collect other than in the stove itself

Not quite sure what point your making here, but I get zero deposits in the stove from my clay liner with a 6" Flexi running through it.