Unusual joints in Firebird combi boiler

The pipes to the heat exchanger in this Firebird Olympic combi boiler have joints of a type I am not used to. The pipe ends have a flat flange which fits against a male threaded brass tube like the tail of a tap[1], but unlike a tap connector they have no continuation of the pipe into the tail. They have been made with various versions of fibre washer and jointing compound, but invariably start leaking. I suspect they may be designed to be used without any washer, but the flanges do not lie flat because the copper pipes are not accurately made to lie in the plane of the joints on the heat exchanger. I feel the copper flanges might bend or break if tightened with no washer.

Does anyone know how these joints should be made, and how to stop them leaking? Many thanks for any comments.

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Reply to
Percy Picacity
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Cracking drawing Percy ! I can see straight away why it leaks. The union nut is much too big for the thread ... :-)

Sorry, couldn't resist that !

Arfa

Reply to
Arfa Daily

"Arfa Daily" wrote in news:sz9mm.6235$ snipped-for-privacy@newsfe15.ams:

Thanks - drawing was never my strong point!

Reply to
Percy Picacity

That's similar to brake pipe unions on cars. Called flared. On brake pipes it has no washer or jointing compound. And has to withstand far higher temperature and pressure. Of course like all such things has to be made correctly.

I'd be inclined to just clean everything and use some Fernox LS-X jointing silicone.

Might also be worth running a fine file across the heat exchanger mating face to make sure it's true and flat.

Reply to
Dave Plowman (News)

"Dave Plowman (News)" wrote in news: snipped-for-privacy@davenoise.co.uk:

That was my immediate idea, but the fact the pipes don't lie in the same plane, and would be significantly twisted to lie flat on the joints is a bit worrying. this could be because some of them have been bent, or perhaps imprecise manufacture. Perhaps I'll give this a go next time one fails. The last (15mm) one I used a rubber washer with filter from a washing machine hose, will be interesting to see if this works for a long time. If it does, I need a source of similarly rigidified (by the filter) 22mm ones.

Reply to
Percy Picacity

That type of joint (not uncommon) certainly requires a washer between the faces.

Could be the wrong type has been used. The tap connector type are too narrow, also may not have been tightened correctly.

Also check that the flange face is not cracked and letting water by.

Reply to
Heliotrope Smith

Then they need to be bent to fit. Use a bending spring and perhaps some heat.

Reply to
Dave Plowman (News)

"Heliotrope Smith" wrote in news:4a99385a snipped-for-privacy@mk-nntp-2.news.uk.tiscali.com:

Thanks, any suggestions as to what the suitable washers are called and where I might get some? Are they likely to be fibre or rubber?

Thanks for any advice!

Reply to
Percy Picacity

"Dave Plowman (News)" wrote in news: snipped-for-privacy@davenoise.co.uk:

That's not easy as they are very short pipes, and one has a side branch brazed on near the end, which branch is too near a bend to use a tee, I presume. But I may get better results if I loosen the joints at the other ends of the pipes (ordinary compression), before refixing the heat exchanger. I want to redo the whole thing when I have firm ideas as to whether to use washers and what type.

Reply to
Percy Picacity

davenoise.co.uk:

You can buy a Regin fibre washer pack with a couple of 1/2" 3/4" and

1" flat washers for a couple of quid. Clean the metal joint surfaces thoroughly and if the threads are scaled wire brush them and put some silicon grease on the threads and the inside of the union nuts so they will tighten without overstressing the things. The pipe ends should lie flat on the protruding threaded part of the heat exchanger. If they don't you should loosen the other ends of the sections so they will. When the Heat exchanger is tightened then retighten the other ends and all should be fine. It is wise to keep an eye on these joints and nip up if required before any weep develops into a leak. The Firebird Combi is a decent unit but the heat exchanger requires monitoring. In hard water areas it sometimes pinholes between the domestic and the sealed system side, however this is not a regular event by any means.

John

Reply to
cynic

cynic wrote in news:b575265a-b2c0-41db-b7d9- snipped-for-privacy@l35g2000vba.googlegroups.co m:

Very helpful, thanks.

That's interesting, because I've got a slow leak somewhere. I suspect the boiler was put together by an amateur (FSVO) because pretty well every joint on it and the central heating circuit has leaked at some point since I moved in. I presume the only way to test it is to disconnect the hot water side and wait a long time, or is it better to take it off and pressurise it in some way? I'll have to check that when I redo it. It's a soft water area, however.

Reply to
Percy Picacity

-2.news.uk.tiscali.com:

On such joints in other locations I've seen fibre. I had one joint on high pressure water that repeatedly leaked after replacing the fibre washer, so I decided to try a rubber one, with doubt, but it worked great and fixed the problem.

I cant help wondering if brazing would be a good option here.

NT

Reply to
NT

Percy Picacity wrote in news:Xns9C7781149F3perspicacity@208.90.168.18:

ends

tightened

Further to this problem, the next time a heat exchanger union leaked I dismantled the relevant piping. With 3 unions coplanar, the fourth was displaced 3 cm axially and 1cm radially, obviously too much to be taken up by adjusting the other joint on the pipe. Adjusting a straight bit of pipework to one of the pumps largely rectified it and I could reassemble it with reduced asymmetrical forces on the unions and new, hopefully not so soft, washers. So far, so good.

Thanks to all for the help.

Reply to
Percy Picacity

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