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Soldering poorly fitting joint - pipe not round, good fill, how?

View the thread, titled "Soldering poorly fitting joint - pipe not round, good fill, how?" which is posted in DIY Plumbing Advice on UK Plumbers Forums.

D

DannyNotAPlumber

Hi,

Short version: I have about 4" of pipe sticking out of a concrete floor in a cupboard. It makes a 45-degree bend as it exists (bent, not with elbows), the last cm before the open end is pretty much straight, but as a result of the bend it is not perfectly round. I mean it is pretty much round cross-section at the very end, but only 1cm down its oval by about 1/2 a mm, and is maybe a full 1mm squished at 15mm. I need to put an elbow on it, the elbow's female end feed overlaps by about 15mm, so while snug with the round end in the depth of the joint, at the point where I will feed solder in, it has a gap of about 1mm on two opposite side. Hope that makes some sense!! Its vertical at that point too.
My concern is that when I feed in the solder, I'm sure the usual capillary action aided by the heat and the properties of the solder will pull it into the deep part of the joint and seal there, at the open end, the vertical position along with the nearly 1mm gap, may allow the solder to 'fall' out and not fill the whole 15mm overlap. I'm pretty sure it will be joined, but I'm not certain it will be a great joint.

More detail:
While I'm not a plumber I did do a lot of study as my enginering trade is not entirely unrelated. It seems that studies have shown that a good joint where the full overlap is well filled does last longer and the theory goes that it being stronger reduces the stress at the ends and reduces any slow work hardening and eventual delamination of the solder.

I have done about 100 joints now, mostly 28mm, about 20 in 22mm and 20 in 15mm, while redoing most of the pipe work around the house, new rads, new main pipes in the loft, a route out to the garage for a heat pump etc. And have pressure tested everything (have got through a lot of olives!) up to 10bar for 24hrs, and have only had one bad joint so far and that was not tricky to understand - I forgot the flux!! So, while my joints weren't pretty to start with and are hardly perfect now (although they are passable), they are sound at least. This particular joint is annoying as I have very little pipe to work with and save for digging out the concrete around it, I have no choice but to braize onto the end of this not-entirely-cylindrical pipe.

I figured others may have had to deal with this before and perhaps the answer is "1mm of out of round is no problem and the solder will still fill and wont all fall out with gravity, surface tension wont fail you until you have at least an eighth of an inch of gap." But maybe the experienced guys here will know that "oh, yeah, that'll all fall out and you'll only get a tiny section of seal, you need to plug round the gap with heat proof putty or silicon after fluxing it and only then will you get a good fill", or perhaps there's some trick. Or maybe the answer will upsetting... "theres no way you'll get a solid joint, its bound to fail, you're better off trying to bend it back round with something forming and some grips, or just bite the bullet and get to work on the concrete Andy Dufresne style and expose enough straight pipe and fix it properly."
I just felt like I should at least ask those who may have experience!!

Thanks in advance for any tips!!!
 
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If the coupler will go on the pipe without force, then it's good to go.
I'd be surprised if at 0.5mm oval that you can get a fitting on the pipe. (rushes out to workshop to conduct experiments, be back later)

If you want more certainty, put a straight coupler (to later be disposed of) on the pipe, lightly squeeze the outside of the coupler with pipe grips whilst turning it to even out the shape.
Check the fit with the other end of the coupler till it fits loosely, if paranoid about the used coupler and it's condition, dispose of it.

If you want more certainty use a Yorshire (solder ring) fitting.

For absolute certainty, break out some concrete and find some decent pipe, but you're probably more likely to get a poor joint when it's partly underground with poor access and previously contaminated with cement.

Another option is an experimental piece, squash a leftover piece of pipe till it's out of roundness matches the subject pipe.
Solder as you would normally, with the fitting in the same orientation and with poor access as the subject piece, then cut and peel open the fitting and see how well the solder took
 
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snowhead said:
If the coupler will go on the pipe without force, then it's good to go.
I'd be surprised if at 0.5mm oval that you can get a fitting on the pipe. (rushes out to workshop to conduct experiments, be back later)

If you want more certainty, put a straight coupler (to later be disposed of) on the pipe, lightly squeeze the outside of the coupler with pipe grips whilst turning it to even out the shape.
Check the fit with the other end of the coupler till it fits loosely, if paranoid about the used coupler and it's condition, dispose of it.

If you want more certainty use a Yorshire (solder ring) fitting.

For absolute certainty, break out some concrete and find some decent pipe, but you're probably more likely to get a poor joint when it's partly underground with poor access and previously contaminated with cement.

Another option is an experimental piece, squash a leftover piece of pipe till it's out of roundness matches the subject pipe.
Solder as you would normally, with the fitting in the same orientation and with poor access as the subject piece, then cut and peel open the fitting and see how well the solder took
Click to expand...
I don't understand it either. The gap is normally tiny, so if you squish the pipe one way, the expansion the other way normally stops it going on. I learned the hard way that the wedge-style deburring tools that nicely get rid of the slight dip as well a the burr, can leave it out of round by a tiny bit if not used carefully and then the pipe wont mate to anything else. Great suggestions with the slight squishing back to round and the test piece. I did do a lot of testing when I first started this endevour about 6 months ago, so am perfectly happy to waste a fitting or two to see how it goes.

I do have one other question, as I seem to have two very sensible people responding already, hope thats okay. I have been pressure testing everything. The only valves on the pipes when doing that testing have been ones I've bought myself with known ratings, so I felt comfortable relying on those. However this particular pipe is for the domestic hot water, and the other end of it is about 5 taps scattered around the ground floor. I'm guessing bathroom taps are not something anyone can guess at, as they are all old. I guess I can just slowly push up the pressure wait till one of the taps starts weeping and then back it off and hope that its high enough to validade this joint.
 
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I've just tried squashing 15mm pipe till the fitting needs light force to fit.
Up to 0.25 mm out of round no force, at or over slight then increased force needed.
I only tried it twice so not particulary scientific,
 
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Use a pair of adjustables and set it to the rough OD of the deformed section. Use them like a pipe slice by tightening them a bit at a time and working them around the pipe simultaneously.

The circumference of the pipe will become rounder as you tighten the jaws and keep turning, there will come a point when you cannot tighten any further but the jaw pressure on the pipe is uniform when turning which'll mean the pipe is round once again.
 
Last edited:
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snowhead said:
I've just tried squashing 15mm pipe till the fitting needs light force to fit.
Up to 0.25 mm out of round no force, at or over slight then increased force needed.
I only tried it twice so not particulary scientific,
Click to expand...
Well those numbers make subjective sense to my experience, so I don't think your method was too bad. it adds to my confusion as to how this bent pipe still fits on. Admittedly its round at the initial insertion point and then gets worse as it slides on, so effectively im sliding it on to an asymmetrical cone, which is probably what is making it possible to get it on at all. 0.7mm feeler gauge fits each side, drats thats a big gap.
 
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Perhaps you've found some old 1/2" imperial thin-walled copper pipe with an OD below 15mm. IIRC, Ireland used to use imperial pipe with an OD of 14.7mm.

Have you considered/ruled out using a socket former?
 
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Chuck said:
Perhaps you've found some old 1/2" imperial thin-walled copper pipe with an OD below 15mm. IIRC, Ireland used to use imperial pipe with an OD of 14.7mm.

Have you considered/ruled out using a socket former?
Click to expand...
Now this is why asking people is a good idea. I had not ruled out using a socket former because I didn't know there was such a thing and am now looking it up... THANK YOU

The only explanation I can think of is that the pipe started off below the standard diameter (22, not 15).
 
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What I do is similar to gmartine, but using water pump pliers to gently squeeze back into shape initially.
If you force a compression nut on first, past where you will be soldering, you can use the visual gap/ tightness of the hole in the centre of the nut as a guide where to squeeze.
It is quite quick to get it near enough to solder!
 
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