Pipes & Chimneys

[Flyfisher]

I'm about to finalise the fitting of a boiler stove in a large inglenook fireplace. The installation requires a heat-leak radiator to be connected that will work by gravity convection in case of a power cut stopping the pump that will normally circulate the hot water through the associated heat store. This will necessitate two pipes to connect the stove to an upstairs radiator and an attic expansion tank.

Rather than break through the side of the inglenook and have visible pipes running up the wall into the upstairs bedroom, I would like to run the pipes up the chimney and drill through into the bedroom, where they would go into a cupboard beside the chimney and therefore remain invisible. From inside the cupboard they can then continue into the attic, so a very neat and tidy installation.

The inglenook is about 2m x 1 m and tapers quite slowly, so is very spacious inside the actual chimney. The stove will be connected to an insulated liner and the pipework can be easily kept well away from the liner. The length of the pipes above the register plate will be less than 2m before existing into the bedroom cupboard.

The installer says that such an installation would be acceptable as far as regulations are concerned, but has advised against running the two pipes inside the chimney because of the residual soot inside it, which he thinks will cause the copper pipes to corrode.

My thinking is that it should be possible to wrap the pipes in a suitable lagging and then cover the lagging with aluminium tape, thus completely covering and protecting the pipes from any soot/tar contamination. Because of the size of the chimney, the pipes would be easily accessible from a step-ladder to do this.

What does the panel think?

 

[paulb33]

Call a chimney sweep?

 

[Lime]

Most of the soot will have lost its acidic content by now.
(I remember having to leave the chimney sweep's soot in a weathered pile in the garden for 6 months before being able to use it as a slug repellent)
I'd wrap the pipes in Denso tape.
Forget the aluminium, if copper is likely to be corroded, it will corrode much faster.

 

[Flyfisher]

The chimney has been swept (as well as such a huge chimney can be!) and there is very little loose soot remaining up there, but of course there is still a lot of blackened mortar and brick that generates the inevitable light rain of sooty dust over time - hence the need for a register plate.

I had not heard of Denso tape but have just read the datasheet and it would seem to be the purpose-made solution for such things.

Another problem solved by the PPUK forum! Many thanks Lime.

 

[Lime]

The chimney has been swept (as well as such a huge chimney can be!) and there is very little loose soot remaining up there, but of course there is still a lot of blackened mortar and brick that generates the inevitable light rain of sooty dust over time - hence the need for a register plate.

I had not heard of Denso tape but have just read the datasheet and it would seem to be the purpose-made solution for such things.

Another problem solved by the PPUK forum! Many thanks Lime.

It is very useful stuff.
I use it on my Land Rovers between dissimilar metals before clamping/bolting/riveting down.
It puts a stop to galvanic corrosion as well as keeping out water.

Just in case there is some confusion as to what I mean, this is it:-
http://www.toolstation.com/shop/Plumbing/Consumables/Petro%20Tape%2010m/d20/sd2711/p72819

or

http://www.ebay.co.uk/itm/like/251159951527?hlpht=true&ops=true&viphx=1&lpid=95&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=95

 

[Feltwell]

Denso tape was used back in my civil engineering days to protect any pipes underground that required corrosion protection, and also used for wrapping around things like the bolt threads where lighting columns are secured to bridge parapets to ensure they never corroded and could be undone in future.

Horrible, sticky, messy stuff but it undoubtedly works!

 

[DJH]

How about copper pipe with prefitted sleeving on it. Peel back to allow soldering any joints and then recover with an insulating tape or similar over the joiners/fittings. Much cleaner and less messy than Denso tape believe me although it's great for cleaning dirt from the hands...

Doug

 

[Flyfisher]

Actually, I've just noticed that the Denso tape temperature range only extends to 55C, which might be exceeded on pipes that will only be about 1m away from the boiler stove.

Perhaps a combination of foam pipe insulation first and then wrapped in Denso tape?

 

[Lime]

If you are worried (which I wouldn't be) I'd paint the pipes.

 

[Feltwell]

Paint is an option, but on reflection I'd agree with Doug and go for coated pipe - I presume it's 15mm you're fitting? Good point about heat and Denso tape.

http://www.plumbcenter.co.uk/en/plu...-tube-15mm-kuterlex-plus-white-coat-6-m-62734

These might be of interest:-

http://www.copper.org/applications/plumbing/techcorner/prevent_corrosion_cu_tube_buried.html

http://www.ukcopperboard.co.uk/lite...on-Tips/Domestic-gas-installation-testing.pdf

 

[Penners]

I think that you'll gain much better heat retention if you enclose the tube in closed cell moulded polyethylene, rather than using pre-insulated tube. Provided the joints in the insulation are properly taped, I also think this will give the copper effective protection from any residual acidity (however slight this risk might be).

http://www.plumbcenter.co.uk/en/plumbing/copper-tube-insulation/center-pipe-insulation-22-mm-x-9-mm-2-m-18628

I certainly subscribe to Lime's recommendation about avoiding contact between the copper and another metal in a potentially acidic environment, which might risk galvanic action.

Just one more thought - in calculating the heat leakage from the system, I don't suppose heat loss from the pipes has been included, has it? If so, then insulating them might have a small effect on the calculation.

 

[Flyfisher]

The pipes are 22mm or 28mm, certainly bigger than 15mm. They are the pipes that connect to the 'heat leak' radiators, which are a necessary safety requirement because the connection to the heat store is via a pumped circuit and if the power (or pump) fails then the heat from the boilerstove must be able to be dissipated via gravity convection. So most of the time the pipes in question shouldn't be too hot.

I think the wraparound type insulation will be fine to protect the pipes from any sooty dust within the chimney, it's just a matter of the best sort of tape to use to keep it in place. I was thinking of aluminium tape because of temperature considerations. I don't see much risk of the aluminium tape coming into contact with the copper pipes, but I take Lime's point about the tape being just as exposed to corrosion as copper pipes. Perhaps ty-raps would be better to hold the pipe insulation in place - there won't be very much of it.

As for heat calculations, I don't think a few metres of bare or insulated pipework will make much difference given the amount of uncertainty of the insulation properties of the house itself. It's all a bit experimental and I won't really know how it all performs until this time next year now.

 

[Me!]

Why not use stainless steel pipe? Stainless is used for flue liners so presumably it must be OK with the soot and the acid.

 

[Flyfisher]

Interesting idea. Actually, I did suggest to our plumber that perhaps he could use galvanised pipe for the short length within the chimney but he didn't seem keen. Stainless would probably be even better.

 

[Flyfisher]

Just to revisit this, I suggested using a length of stainless pipe within the chimney but the plumber still isn't keen.

Am I missing something here? Stainless flexible tap couplings are widely used so there can't be a problem with connecting copper to stainless can there? Surely a standard compression fitting would do the job?

I don't mind insisting he uses stainless but his reluctance raises a feint alarm bell since he has been very good and knowledgeable about all the other wing.

Am I missing something here?

Just to recap, it's a 2m x 1m inglenook fireplace with a boiler-stove. Two 28mm pipes have to be connected to a gravity-operated heat-leak radiator upstairs in case of power failure stopping the pumped circuit taking the hot water from the stove to the heat store. The upstairs bedroom has a cupboard beside the chimney breast, so to hide the pipes I'm suggesting running the two 28mm stainless pipes from the stove through the chimney register plate and up one corner of the open flue to exit inside the bedroom cupboard. Inside the chimney, the pipes will be covered.

The alternative is to route the pipes through the side of the inglenook and then up the wall into the bedroom cupboard, so very visible and intrusive.

 

[Me!]

Does the plumber say why he isn't keen on doing it?
I know a tame chemical engineer, I'll consult him and report back.

 

[Flyfisher]

It seems to the be the basic idea of running the pipes inside the chimney, though he has admitted there is no regulation problem.

It would be a run of less than 2m and the chimney is so large that access is very easy using a step ladder and, as you have pointed out, there is already a stainless liner installed.

It would be interesting to know what your chemical engineer friend thinks. Many thanks.

 

[Me!]

He says he can't think of any reason why it would be a problem to use stainless steel water pipes going up the chimney stack.

He also says that it should be fine joining the stainless steel back to copper again as long as you limit the difference in the anodic index between the two metals to 0.15V or less http://en.wikipedia.org/wiki/Galvanic_corrosion#Anodic_index so that would require the use of a stainless steel grade with at least 18% chromium, so 302, 304, 309 etc (http://www.bosunsupplies.com/StainlessInfo2/).

Edited -
PS. He has just added that using a brass olive against the stainless pipe would obviously be better than using a copper one.

 

[Flyfisher]

Wonderful - great answer and with references to explain the background! Thank you very much for that.

Is there no limit to the depth of PPUK knowledge?

 

[Penners]

I suggested using a length of stainless pipe within the chimney but the plumber still isn't keen.

Did he tell you exactly why he isn't keen? Is it perhaps time to remind him who pays the bill?! :wink:

I can certainly see no technical reason why you can use stainless steel pipe. As you correctly observe, the joint between stainless and copper can be made with a compression fitting (assuming that a Speedfit joint is unacceptable for this application). Provided the correct additive is put into the water, galvanic action shouldn't be a problem.