Woodburner – water dripping down flue

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  • Woodburner – water dripping down flue
  • mattrgee
    Member

    Hi all,

    We had a woodburner fitted during the summer, all above board, certificates issued etc Not long afterwards, during heavy rain, water started leaking from the top of the flue where it meets the register plate There is a rope ‘seal’ around the top of the flue. I spoke to the installer who said this was rare but normal and during heavy rain, water will come down the liner and potentially find it’s way through the rope seal.

    3 months later and it’s raining outside and we’re having to wipe the flue every few minutes to catch the long, black drips that are running down it.

    Is this normal? Have I been fobbed off?

    Thanks.

    twinw4ll
    Member

    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.

    mattrgee
    Member

    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.

    Premier Icon mrwhyte
    Subscriber

    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?

    mattrgee
    Member
    Premier Icon Squirrel
    Subscriber

    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.

    sharkbait
    Member

    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.

    wrightyson
    Member

    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.

    neilnevill
    Member

    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.

    sharkbait
    Member

    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

    mattrgee
    Member

    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:

    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?

    tjagain
    Member

    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

    josh145
    Member

    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

    mattrgee
    Member

    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.

    Premier Icon kcal
    Subscriber

    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.

    Premier Icon bedmaker
    Subscriber

    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

    neilnevill
    Member

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

    Bits n Bobs: Sump adaptor

    Premier Icon bedmaker
    Subscriber

    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…

    mattrgee
    Member

    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.

    Premier Icon spooky_b329
    Subscriber

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

    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)

    neilnevill
    Member

    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.

    twinw4ll
    Member

    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.

    twinw4ll
    Member

    Contact HETAS they will come out and inspect the installation.

    trail_rat
    Member

    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.

    Premier Icon bedmaker
    Subscriber

    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

    mattrgee
    Member

    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

    Thanks, which one of those cowls did you use?

    Premier Icon bedmaker
    Subscriber

    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 🙂

    sharkbait
    Member

    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.

    mattrgee
    Member

    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.

    globalti
    Member

    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.

    trail_rat
    Member

    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 ?

    mattrgee
    Member

    I’m not burning larch.

    globalti
    Member

    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.

    neilnevill
    Member

    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.

    mattrgee
    Member

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

    No, internal wall, centre of the house.

    globalti
    Member

    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.

    trail_rat
    Member

    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.

    twinw4ll
    Member

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

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