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Stand back, she's gunna blow......

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Stand back, she's gunna blow......

Postby toolsntat » 07 Oct 2021, 02:11

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Lovely start to the day doing a fitted wardrobe then cut back the carpet to expose a dry but sunken and water stained chipboard floor :shock:
Hey up me-duk, I think there's summat up here....
Cheers Andy
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Re: Stand back, she's gunna blow......

Postby Mike G » 07 Oct 2021, 06:49

I wonder how long that's been leaking.
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Re: Stand back, she's gunna blow......

Postby Doug » 07 Oct 2021, 07:23

Ain’t it a pain Andy, there’s always something to bugger your day up.
More than likely imperfections in the copper that break down & cause a very slow weep judging by the build up of corrosion.

My pet hate is muppets who put copper pipe in screeds without any protection, earlier in the year I fitted a large laminate floor while taking up the old flooring there was a 6m run of new clearly damp concrete, this held the job up for a while.

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Re: Stand back, she's gunna blow......

Postby Phil Pascoe » 07 Oct 2021, 07:32

I found a 15mm copper pipe like that in my old house with pin holes through it ............ it was a gas pipe. It wasn't lagged where it entered the house through an air brick and it had corroded there.
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Re: Stand back, she's gunna blow......

Postby PAC1 » 07 Oct 2021, 08:19

About 10-15 years ago there was a bad batch of copper pipes which were renowned for pinhole failures. there were thousands of installations that needed replacing.
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Re: Stand back, she's gunna blow......

Postby novocaine » 07 Oct 2021, 08:26

it's been overpulled then pushed back, work hardening the already thinned outside radius wall. Along with possible impurities it's going to leak. it's why tube benders became so popular (before plastic) you could pull a bend with minimal stress and thinning and assuming you weren't a dope, over bending was almost impossible. this bend is a spring bend (you can see the wrinkly knickers on the pipe behind) which means the bend isn't uniform and the pipewall gets drawn thinner in different places.

guessing it's CH, so add in cyclic fatigue. I also reckon (but can't say for sure) that the pipe is being clamped tight either side of the bend by joists and floor boards so it can't move.

looking at the boarding below, it's been looked at before, but it's had a bit of bung stuck on the pipe and the "plumper" has mad a hasty retreat.
Last edited by novocaine on 07 Oct 2021, 09:32, edited 1 time in total.
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Re: Stand back, she's gunna blow......

Postby Phil Pascoe » 07 Oct 2021, 09:00

^^ ... so it can't move?

We had endless problems some years ago with stainless pipework put in in the mid '60s during the South African copper embargo. So many pinholes it just had to be torn out. 100s of metres of it.
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Re: Stand back, she's gunna blow......

Postby novocaine » 07 Oct 2021, 09:31

EDIT: I just realised you were correcting my typo for me not asking. sorry and thanks for correcting it. Ignore the granny sucking eggs below. I'm not deleting it though, because it's got a pretty drawing.


Pipes expand/contact as they heat and cool in an axial direction. when you have a bend like this the pipe coming in wants to push the bend (and thus the pipe round the corner) in that direction.
if you don't let it move, the expansion is restricted and the bend has to deform to allow for the movement.
you can get away with some of it if depending on the length of pipe between the constraints, I'm guessing here but I reckon the pipe hits a joist 10" after the bend (down on the first picture) and it's tight up against the notch wall that was cut for it. the inner pipe isn't and will be able to slide on the joist to allow the movement to be taken up by the pipework.

rubbish drawing but something like this.

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Re: Stand back, she's gunna blow......

Postby Andyp » 07 Oct 2021, 09:38

A damp patch in the ceiling once led us to find a rusty metal meat tray under the floorboards and under the fitted carpet catching a small drip from a water pipe. God only knows how long it had been there, I think we must have been in the house 5 or 6 years by then.
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cheers
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Re: Stand back, she's gunna blow......

Postby Eric the Viking » 07 Oct 2021, 10:23

Andy (TnT), is that the hot or cold pipe?

And am I the only one who anneals drawn copper pipe before doing awkward bends?

It's not just poor quality copper - we have Sheffield stainless cutlery (fairly recent) that has rust spots (and microscopic pitting) from the dishwasher.
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Re: Stand back, she's gunna blow......

Postby novocaine » 07 Oct 2021, 10:49

Eric the Viking wrote:Andy (TnT), is that the hot or cold pipe?

And am I the only one who anneals drawn copper pipe before doing awkward bends?

It's not just poor quality copper - we have Sheffield stainless cutlery (fairly recent) that has rust spots (and microscopic pitting) from the dishwasher.


annealing shouldn't be needed on fresh shiny copper, it's annealed after being drawn.
on old stuff that you've had floating around for a few years, yer I might consider it. but I have a pipe bender that supports the pipe and uses a form to prevent overworking so meh. I was playing with it at the weekend to fit the last rad to our house. 2 runs, not a joint in sight. no one will ever notice it, but I know it's done well.
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Re: Stand back, she's gunna blow......

Postby Lurker » 07 Oct 2021, 11:20

Andy (TnT) ,
I hope your client fully appreciates how much money and aggravation you have just saved them.
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Re: Stand back, she's gunna blow......

Postby jimmy s » 07 Oct 2021, 22:48

Normal plumbing R250 (formerly table X) copper is normally referred to as half hard copper. I don't know if its a different grade to what was table Y copper, now R220 grade, or if one is normalised and the other annealed?

The half hard stuff does bend fine with pipe benders though.
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