wood burning stove again - taping the joints in the pipes

[Robina]

Hi,

We have been getting to grips with having tarry stuff leaking out of the joints on the flue on our wood burning stove.  I have read all the posts on this subject in the forum and I think that our only real solution is to insulate the pipe all the way up the chimney.  This is apparently quite an expensive job (we are not DIYers for this kind of thing!)  so while we wait we want to minimise the leakage. 

The stove is free-standing and the flue rises straight out of the top and then does a 90 degree bend into the chimney.  The tarry drips come from where the joint of the horizontal pipe meets the vertical pipe and also from the joints between sections of the vertical pipe.  This christmas was actually a lot better than last - presumably because our wood has now had a year to dry out!  My question is: can we use some kind of heat-resistant tape to seal the joints between sections of pipe?  I've not seen it done on stove pipes but it is used for car exhausts etc.  Thanks.

Robina

[Weedon]

There is tape available at the Brico's, it's called Bande Alu Autocollante.  At least I bought some for that very purpose but have yet to open the pack, so unless somebody else here says differently, that's the stuff.

[clarksinfrance]

|Robina, I am assuming you are using either single (1mm thick) or twin walled (insulated) enamelled or stainless steel tubes? as opposed to twin-walled flexible tube? If so the sockets should all point skyward, so that if any condensates run down the inside, they stay inside. It may be a case of inverting the tubes?

[John A]

... and I fully concur with Nick because I've just done that, and it's cured my immediate problem. For the longer term I need to find a way of reducing the amount of tar generated, but for now it all runs back into the stove to be reburned and we've got rid of the terrible smell. The tar is actually quite corrosive - earlier on it caused a hole to appear in one of our pipes at the seam, which allowed (poisonous?) gasses to escape. We used some of that silvery Scotch tape as a temporary fix for that.

[robbie]

[quote]and then does a 90 degree bend into the chimney[/quote]

I was advised not to have 90 degree bends in the flue and try to keep it to max of 22.5, 45 as an absolute max...... now I am confused.

Maybe this is part of the issue, if the flue did not go horizontal, then the tarry goo would trickle into the burner and be reburnt..... or do I have it all wrong [8-)]

[Robina]

Thanks for all the advice.  I did wonder about inverting the tubes but the installer (or rather, his wife, as I have never spoken to the installer in person) said that if the tubes were inverted you would get smoke rising out of the joins rather than tar dripping down.  What I really want to do is seal the joins in a flexible way to allow for the necessary expansion and contraction and thought the 'autocollant' tape would do the job -  albeit not very elegantly.

As for the 90 degrees - I don't know either - I saw the comments about that but the installer is the local professional so he should know. 

Robina

[LesFlamands]

Sockets must be upwards (regulations). 90 degree bends are not a good idea except at the back of the stove but best use a Tee with bouchon for easy cleaning. If the flue draws correctly, i.e. it is long enough, clears the roof by a decent margin and is insulated where it needs to be then you won't get any smoke leaks or condensation unless the fuel is wet. Taping the flue won't work against condensation. taping is only used as a belt and braces on gas flues.

You installer should be shot, or banned, or something.

[Mutiara]

When you say sockets can you explain in more detail. Ie; Should the tube below slot inside the next one up or should the higher one slot into the lower one?

[LesFlamands]

Female end upwards

[robbie]

[quote]As for the 90 degrees - I don't know either - I saw the comments about

that but the installer is the local professional so he should know[/quote]

I was led to believe that horizontal flues were fine if the outlet from the burner was on the back and not the top......

[Monika]

We had a brandnew woodburner installed 18 months ago and had a terrible tar problem, it was coming out of all the joints. After a lot of research and good advice on this forum I went to the installer and he turned the flue around (having to buy some extra connecting sockets), now the female ends are looking towards the ceiling and the male ones towards the floor! And the problem is solved, no more tar!

[raindog]

[quote user="robbie"][quote]As for the 90 degrees - I don't know either - I saw the comments about

that but the installer is the local professional so he should know[/quote]

I was led to believe that horizontal flues were fine if the outlet from the burner was on the back and not the top......

[/quote]

We've had a 90° bend coming out of the back of our stove for ten years and it works perfectly.

I recently helped a friend fit a woodburner, and when we went to buy the tubing, the salesman explained that the regs have changed and the joins are now female pointing upwards and male slotting in from above, and that's how the tee's are made so you can't get it wrong.

I've still got me old system tho' [:)]

[clarksinfrance]

It is perfectly acceptable to have a 90degree bend from an outlet at the back of a wood burner, but there are regulations, on the length of horizontal run, (can't remember the length at this point in time). It is advised in all regulations I have come across to keep any change in direction as shallow as possible, and certainly no more than 2 changes, in a flue. 22.5 degrees are indeed better than 45degrees. Female ends point up, male down; always been this way,  Use Mortiere Refractaire (sp??) to seal joints.

[raindog]

[quote user="clarksinfrance"] Female ends point up, male down; always been this way,

[/quote]

Not at all, the proof being that my 90° elbow slots straight onto the adaptor on the back of the stove with it's male end upwards.

[John A]

We have had loads of trouble with a downward-pointing socket at the join with the stove collar. This was put in by a local installer, replaced in the same way by another local installer. Also the man at the Supra helpdesk agreed that the first pipe should go around the outside, rather than in the inside, of the collar.

This seems very unsatisfactory to me because it allows the tar to run out of the joint onto the top of the stove, instead of into the stove to be reburnt. The Supra Alsace collar is 150mm external and 147 internal, so we had to get a reducer to go into 147 mm.

I wonder if Supra stoves are unusual in this respect - does anyone else have similar trouble with them?

[raindog]

The fact is, if everything's set up correctly, and your upper chimny is insulated in some way, you shouldn't be having the tar problem anyway.

[LesFlamands]

[quote user="raindog"]The fact is, if everything's set up correctly, and your upper chimny is insulated in some way, you shouldn't be having the tar problem anyway.
[/quote]

Yes, and the fuel is dry (hardwood)

Regarding horizontal runs, going horizontally through a stone wall is sometimes unavoidable. If you ensure there is decent access into the pipe (external Tee piece) this will simplify cleaning out which will probably be required at least once a month for a stove in full time use.

Stoves that are designed with a male spigot for the flue connection are useless (i.e.most French stoves)

[clarksinfrance]

Have found the distance allowed for horizontal runs, its 150mm, but must not have more than 2mm deflection. to go through some thick walls (1m in some longeres), the flue should be run through on an angle, as 150mm is obviously too short. 45 degrees is what is usually applied.